Operational amplifier circuit
By integrating a Zener diode and transistor-based constant voltage circuit, the operational amplifier circuit addresses frequency-dependent crosstalk issues, ensuring consistent reference voltage and improved crosstalk performance across a broader frequency range.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- PANASONIC AUTOMOTIVE SYST CO LTD
- Filing Date
- 2024-11-08
- Publication Date
- 2026-05-20
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Conventional operational amplifier circuits face challenges in achieving desired crosstalk performance below certain frequencies, particularly at 100 Hz, due to frequency-dependent reference voltage fluctuations, which affect crosstalk between operational amplifiers.
Incorporating a Zener diode and transistor configurations to create a constant voltage generation circuit that reduces output impedance, ensuring the reference voltage remains constant across various frequencies, thereby reducing crosstalk between operational amplifiers.
The proposed solution effectively maintains the reference voltage constant, meeting the required crosstalk performance of 60 dB across the targeted frequency domain, including frequencies below 500 Hz.
Smart Images
Figure 2026083916000001_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present invention relate to an operational amplifier circuit.
Background Art
[0002] Conventionally, as an example of an operational amplifier circuit, an operational amplifier circuit for audio is known. In such an operational amplifier circuit, there is one having a plurality of operational amplifier sections to correspond to a plurality of audio channels. In such an operational amplifier circuit, by inputting an input signal to only one of the operational amplifiers and setting the other operational amplifiers in a non-input state and comparing the outputs of each operational amplifier, it is possible to perform a crosstalk performance evaluation.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
[0005] The operational amplifier circuit of the embodiment comprises a reference voltage generation circuit connected to a single power supply that generates and outputs a reference voltage signal, and a plurality of operational amplifier circuit sections, each having an operational amplifier that operates on the single power supply, wherein the output impedance of the reference voltage generation circuit is set so that the voltage fluctuation amount of the reference voltage signal is less than or equal to a predetermined value. [Brief explanation of the drawing]
[0006] [Figure 1] Figure 1 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the first embodiment. [Figure 2] Figure 2 shows an example of the configuration of a conventional differential input operational amplifier circuit. [Figure 3] Figure 3 is an explanatory diagram of the frequency characteristics of a conventional reference voltage VREF. [Figure 4] Figure 4 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the first embodiment. [Figure 5] Figure 5 is an explanatory diagram of an example configuration of the operational amplifier circuit of the second embodiment. [Figure 6] Figure 6 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the second embodiment. [Figure 7] Figure 7 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the third embodiment. [Figure 8] Figure 8 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the third embodiment. [Figure 9] Figure 9 is an explanatory diagram of an example configuration of the operational amplifier circuit of the fourth embodiment. [Figure 10] Figure 10 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the fourth embodiment. [Figure 11] Figure 11 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the fifth embodiment. [Figure 12] Figure 12 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the fifth embodiment. [Figure 13]FIG. 13 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the sixth embodiment. [Figure 14] FIG. 14 is a diagram showing the configuration of a conventional non-inverting input operational amplifier circuit. [Figure 15] FIG. 15 is an explanatory diagram of the simulation result of the circuit of FIG. 14. [Figure 16] FIG. 16 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the seventh embodiment. [Figure 17] FIG. 17 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the eighth embodiment. [Figure 18] FIG. 18 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the ninth embodiment. [Figure 19] FIG. 19 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the tenth embodiment. [Figure 20] FIG. 20 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the eleventh embodiment. [Figure 21] FIG. 21 is an explanatory diagram of the frequency characteristics of the reference voltage VREF when a predetermined voltage is applied. [Figure 22] FIG. 22 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the twelfth embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0007] Hereinafter, an operational amplifier circuit according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. [1] First Embodiment FIG. 1 is an explanatory diagram of a configuration example of an operational amplifier circuit according to the first embodiment. The operational amplifier circuit 10 constitutes a 4-input / 4-output differential input amplifier circuit, and includes a first operational amplifier section 11, a second operational amplifier section 12, a third operational amplifier section 13, a fourth operational amplifier section 14, a resistor 105, and a Zener diode 501.
[0008] In the above configuration, the first to fourth operational amplifier sections 11 to 14 constitute a differential input amplifier circuit.
[0009] The first operational amplifier section 11 includes a resistor 101, a resistor 102, a feedback resistor 103, a resistor 104, a capacitor 107, a capacitor 108, and a first operational amplifier 110. In the above configuration, resistors 101 and 102 function as input resistors, and capacitors 107 and 108 function as input capacitors.
[0010] One end of resistor 101 is connected to the inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 107. One end of resistor 102 is connected to the non-inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 108.
[0011] One end of the feedback resistor 103 is connected to the output terminal of the first operational amplifier 110, and the other end is connected to one end of resistor 101. One end of resistor 104 is connected to the non-inverting input terminal of the first operational amplifier 110, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501.
[0012] One end of resistor 105 is connected to the power supply Vcc, and the other end is connected to the cathode terminal of Zener diode 501. One end of capacitor 107 is connected to the first inverting input terminal IN1-, and the other end is connected to the other end of resistor 101.
[0013] One end of capacitor 108 is connected to the first non-inverting input terminal IN1+, and the other end is connected to the other end of resistor 102. The first operational amplifier 110 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0014] The first operational amplifier 110 has an inverting input terminal connected to one end of resistor 101, a non-inverting input terminal connected to one end of resistor 102, and an output terminal connected to the output terminal OUT1 of the first operational amplifier section 11.
[0015] In the above configuration, the voltage at the connection point between resistor 105 and the cathode terminal of Zener diode 501 is set to the reference voltage VREF.
[0016] The second operational amplifier section 12 includes a resistor 201, a resistor 202, a feedback resistor 203, a resistor 204, a capacitor 207, a capacitor 208, and a second operational amplifier 210. In the above configuration, resistors 201 and 202 function as input resistors, and capacitors 207 and 208 function as input capacitors.
[0017] One end of resistor 201 is connected to the inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 207. One end of resistor 202 is connected to the non-inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 208.
[0018] One end of the feedback resistor 203 is connected to the output terminal of the second operational amplifier 210, and the other end is connected to one end of resistor 201. One end of resistor 204 is connected to the non-inverting input terminal of the second operational amplifier 210, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501.
[0019] One end of capacitor 207 is connected to the second inverting input terminal IN2-, and the other end is connected to the other end of resistor 201.
[0020] One end of capacitor 208 is connected to the second non-inverting input terminal IN2+, and the other end is connected to the other end of resistor 202. The second operational amplifier 210 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0021] The third operational amplifier section 13 includes a resistor 301, a resistor 302, a feedback resistor 303, a resistor 304, a capacitor 307, a capacitor 308, and a third operational amplifier 310. In the above configuration, resistors 301 and 302 function as input resistors, and capacitors 307 and 308 function as input capacitors.
[0022] One end of resistor 301 is connected to the inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 307. One end of resistor 302 is connected to the non-inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 308.
[0023] One end of the feedback resistor 303 is connected to the output terminal of the third operational amplifier 310, and the other end is connected to one end of resistor 301. One end of resistor 304 is connected to the non-inverting input terminal of the third operational amplifier 310, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501.
[0024] One end of capacitor 307 is connected to the third inverting input terminal IN3-, and the other end is connected to the other end of resistor 301.
[0025] One end of capacitor 308 is connected to the third non-inverting input terminal IN3+, and the other end is connected to the other end of resistor 302. The third operational amplifier 310 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0026] The fourth operational amplifier section 14 includes a resistor 401, a resistor 402, a feedback resistor 403, a resistor 404, a capacitor 407, a capacitor 408, and a fourth operational amplifier 410. In the above configuration, resistors 401 and 402 function as input resistors, and capacitors 407 and 408 function as input capacitors.
[0027] One end of resistor 401 is connected to the inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 407. One end of resistor 402 is connected to the non-inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 408.
[0028] One end of the feedback resistor 403 is connected to the output terminal of the fourth operational amplifier 410, and the other end is connected to one end of resistor 401. One end of resistor 404 is connected to the non-inverting input terminal of the fourth operational amplifier 410, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501.
[0029] One end of capacitor 407 is connected to the fourth inverting input terminal IN4-, and the other end is connected to the other end of resistor 401.
[0030] One end of capacitor 408 is connected to the fourth non-inverting input terminal IN4+, and the other end is connected to the other end of resistor 402. The fourth operational amplifier 410 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0031] Before providing a detailed description of the embodiment, we will now explain the problems with the conventional approach. Figure 2 shows an example of the configuration of a conventional differential input operational amplifier circuit. In Figure 2, the same reference numerals are used for parts that are the same as those in Figure 1.
[0032] When a voltage VIN1+ is applied to the first non-inverting input terminal IN1+ of the first operational amplifier section 11 of the conventional differential input operational amplifier circuit 10P, and a voltage VIN1- is applied to the first inverting input terminal IN1- of the first operational amplifier section 11, the output voltage VOUT1 of the output terminal OUT1 of the first operational amplifier 110 is given by equations (1) and (2).
[0033]
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[0034]
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[0035] Furthermore, the reference voltage VREF when a voltage VIN1+ is applied to the first non-inverting input terminal IN1+ is given by equations (1) and (3).
[0036]
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[0037] Figure 3 is an explanatory diagram of the frequency characteristics of the reference voltage VREF when a predetermined voltage is applied. Figure 3 shows an example of the frequency characteristics (simulated values) when -18.5 dBV (θ=0 deg) is applied to the first non-inverting input terminal IN1+ and -18.5 dBV (θ=180 deg) is applied to the first inverting input terminal IN1-. Here, θ is the phase of voltage VIN1+ and voltage VIN1-. The dotted line represents the output voltage VOUT1 of the output terminal OUT1 of the first operational amplifier 110, and the solid line represents the voltage of the reference voltage VREF.
[0038] In this case, if the second non-inverting input terminal IN2+ and the second inverting input terminal IN2- of the second operational amplifier section 12, the third non-inverting input terminal IN3+ and the third inverting input terminal IN3- of the third operational amplifier section 13, and the fourth non-inverting input terminal IN4+ and the fourth inverting input terminal IN4- of the fourth operational amplifier section 14 are left blank, the voltage of the reference voltage VREF will be equal to the voltages VOUT2, VOUT3, and VOUT4 of the output terminals OUT2, OUT3, and OUT4.
[0039] In other words, this results in crosstalk from the first non-inverting input terminal IN1+ to the second operational amplifier 210, the third operational amplifier 310, and the fourth operational amplifier 410.
[0040] In the example shown in Figure 3, the reference voltage VREF exhibits a 6dB / octave downward-sloping frequency response due to a first-order low-pass filter consisting of resistors 104, 105, 106 and capacitor 109.
[0041] Therefore, when the required crosstalk performance was set to 60 dB (shown as the dashed line TH in Figure 3), the requirement was met at 1 kHz, but there was a problem in that the required crosstalk performance could not be met below 500 Hz (especially at 100 Hz).
[0042] Figure 4 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the first embodiment. As shown in Figure 1, the reference voltage generation circuit is configured using a Zener diode 501 that functions as a constant voltage element, so the output impedance of the reference voltage generation circuit can be sufficiently reduced.
[0043] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, the required crosstalk performance (60 dB in the example above) can be met.
[0044] As described above, according to this first embodiment, in an operational amplifier circuit comprising a plurality of operational amplifier circuit sections, each having a differential input operational amplifier that operates on a single power supply, crosstalk between operational amplifiers can be reduced.
[0045] [2] Second embodiment Figure 5 is an explanatory diagram of an example configuration of the operational amplifier circuit of the second embodiment. In Figure 5, the same reference numerals are used for parts that are the same as those in the first embodiment of Figure 1. The operational amplifier circuit 10A, like the operational amplifier circuit 10, constitutes a 4-input / 4-output differential input amplifier circuit. The operational amplifier circuit 10A comprises a first operational amplifier section 11, a second operational amplifier section 12, a third operational amplifier section 13, a fourth operational amplifier section 14, and a constant voltage circuit CV1.
[0046] In the above configuration, the constant voltage circuit CV1 functions as a reference voltage generation circuit. Furthermore, the first operational amplifier section 11, the second operational amplifier section 12, the third operational amplifier section 13, and the fourth operational amplifier section 14 have the same configuration as in the first embodiment, so a detailed explanation of them will be omitted.
[0047] The constant voltage circuit CV1 includes a Zener diode 501, a first transistor 502, a second transistor 503, a resistor 105, and resistors 504 and 505. The anode terminal of the Zener diode 501 is grounded. The first transistor 502 has its emitter terminal connected to the cathode terminal of the Zener diode 501, and its collector terminal connected to the other end of the resistor 105.
[0048] The second transistor 503 has its collector terminal connected to the power supply Vcc, its base terminal connected to the collector terminal of the first transistor 502, and its emitter terminal connected to resistors 104, 204, 304, 404, and 504, which serve as the output terminal for the reference voltage VREF.
[0049] Resistor 504 has one end connected to the emitter terminal of the second transistor 503 and the other end connected to the base terminal of the first transistor 502. Resistor 505 has one end connected to the connection point between resistor 504 and the base terminal of the first transistor 502, and the other end is grounded.
[0050] Figure 6 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the second embodiment. In the above configuration, since most of the emitter current of the second transistor 503 flows into the resistor 504, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1+. The output impedance of the constant voltage circuit CV1, which serves as a reference voltage generation circuit, can be sufficiently reduced.
[0051] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, the required crosstalk performance (60 dB in the example above) can be met.
[0052] As described above, according to this second embodiment, similar to the first embodiment, in an operational amplifier circuit comprising a plurality of operational amplifier circuit sections, each having a differential input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0053] [3] Third embodiment Figure 7 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the third embodiment. In Figure 7, the same reference numerals are used for parts that are the same as those in the first embodiment in Figure 1 and the second embodiment in Figure 5.
[0054] The operational amplifier circuit 10B, like the operational amplifier circuit 10, constitutes a 4-input / 4-output differential input amplifier circuit. The operational amplifier circuit 10B comprises a first operational amplifier section 11, a second operational amplifier section 12, a third operational amplifier section 13, a fourth operational amplifier section 14, and a constant voltage circuit CV2.
[0055] In the above configuration, the constant voltage circuit CV2 functions as a reference voltage generation circuit. Furthermore, the first operational amplifier section 11, the second operational amplifier section 12, the third operational amplifier section 13, and the fourth operational amplifier section 14 have the same configuration as in the first embodiment, so a detailed explanation of them will be omitted.
[0056] The constant voltage circuit CV2 includes a Zener diode 501, a first transistor 502, a resistor 105, a resistor 106, and a capacitor 109. The anode terminal of the Zener diode 501 is grounded. The first transistor 502 has its emitter terminal connected to the cathode terminal of the Zener diode 501, and its collector terminal connected to the power supply Vcc.
[0057] Resistor 105 has one end connected to the power supply Vcc and the other end connected to the base terminal of the first transistor 502. Resistor 106 has one end connected to the connection point between the base terminal of the first transistor 502 and the other end of resistor 105, and the other end is grounded. Capacitor 109 is connected in parallel with resistor 106.
[0058] Figure 8 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the third embodiment. In the above configuration, since most of the emitter current of the first transistor 502 flows into the Zener diode 501, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1+. The output impedance of the constant voltage circuit CV2, which serves as a reference voltage generation circuit, can be sufficiently reduced.
[0059] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, similar to the embodiments described above, the required crosstalk performance (60 dB in the above example) can be met.
[0060] As described above, according to this third embodiment, similar to the first and second embodiments, in an operational amplifier circuit comprising a plurality of operational amplifier circuit sections, each having a differential input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0061] [4] Fourth Embodiment Figure 9 is an explanatory diagram of an example configuration of the operational amplifier circuit of the fourth embodiment. In Figure 9, the same reference numerals are used for parts that are the same as those in the first embodiment in Figure 1, the second embodiment in Figure 5, and the third embodiment in Figure 7.
[0062] The operational amplifier circuit 10C, like the operational amplifier circuit 10, constitutes a 4-input / 4-output differential input amplifier circuit. The operational amplifier circuit 10C comprises a first operational amplifier section 11, a second operational amplifier section 12, a third operational amplifier section 13, a fourth operational amplifier section 14, and a constant voltage circuit CV3.
[0063] In the above configuration, the constant voltage circuit CV3 functions as a reference voltage generation circuit. Furthermore, the first operational amplifier section 11, the second operational amplifier section 12, the third operational amplifier section 13, and the fourth operational amplifier section 14 have the same configuration as in the first embodiment, so a detailed explanation of them will be omitted.
[0064] The constant voltage circuit CV3 comprises a first transistor 502, a resistor 105, a resistor 106, a capacitor 109, and a resistor 506. The first transistor 502 has its emitter terminal connected to one end of resistor 506 and its collector terminal connected to the power supply Vcc. Resistor 105 has one end connected to the power supply Vcc and the other end connected to the base terminal of the first transistor 502.
[0065] Resistor 106 has one end connected to the connection point between the base terminal of the first transistor 502 and the other end of resistor 105, and the other end is grounded. Capacitor 109 is connected in parallel with resistor 106. The other end of resistor 506 is grounded.
[0066] In the above configuration, the first transistor 502 and the resistor 506 constitute an emitter follower.
[0067] Figure 10 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the fourth embodiment. In the above configuration, since most of the emitter current of the first transistor 502 flows into the resistor 506, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1+.
[0068] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation.
[0069] As a result, as shown in Figure 10, the required crosstalk performance (60 dB in the above example) can be met, similar to each of the embodiments described above.
[0070] As described above, according to this fourth embodiment, similar to the first, second, and third embodiments, in an operational amplifier circuit comprising a plurality of operational amplifier circuit sections, each having a differential input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0071] [5] Fifth embodiment Figure 11 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the fifth embodiment. In Figure 11, the same reference numerals are used for parts that are the same as those in the first embodiment in Figure 1, the second embodiment in Figure 5, the third embodiment in Figure 7, and the fourth embodiment in Figure 9.
[0072] The operational amplifier circuit 10D, like the operational amplifier circuit 10, constitutes a 4-input / 4-output differential input amplifier circuit. The operational amplifier circuit 10D comprises a first operational amplifier section 11, a second operational amplifier section 12, a third operational amplifier section 13, a fourth operational amplifier section 14, and a constant voltage circuit CV4.
[0073] In the above configuration, the constant voltage circuit CV4 functions as a reference voltage generation circuit. Furthermore, the first operational amplifier section 11, the second operational amplifier section 12, the third operational amplifier section 13, and the fourth operational amplifier section 14 have the same configuration as in the first embodiment, so a detailed explanation of them will be omitted.
[0074] The constant voltage circuit CV4 has the same function as the constant voltage circuit CV3 of the fourth embodiment, and instead of an emitter follower circuit composed of the first transistor 502 and resistor 506, it is equipped with an operational amplifier 510. Resistor 105 has one end connected to the power supply Vcc and the other end connected to one end of resistor 106.
[0075] Resistor 106 has one end connected to the other end of resistor 105, and the other end is grounded. The non-inverting input terminal of the op-amp 510 is connected to the connection point between resistors 105 and 106, and its output terminal is connected to the inverting input terminal. Capacitor 109 is connected in parallel with resistor 106.
[0076] In the above configuration, the operational amplifier 510 has a low output impedance, similar to the emitter follower in the fourth embodiment.
[0077] Figure 12 is an explanatory diagram of the frequency characteristics of the reference voltage VREF in the fifth embodiment. The reference voltage VREF can be effectively kept constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, the required crosstalk performance (60 dB in the example above) can be fully met (230 dB in the example shown in Figure 12).
[0078] As described above, according to this fifth embodiment, similar to the first, second, third, and fourth embodiments, in an operational amplifier circuit comprising multiple operational amplifier circuit sections, each having a differential input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0079] [6] Sixth Embodiment While the above embodiments described differential input operational amplifier circuits, this sixth embodiment is an embodiment of a non-inverting input operational amplifier circuit.
[0080] Figure 13 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the sixth embodiment. In Figure 13, parts similar to those in the first embodiment of Figure 1 are denoted by the same reference numerals.
[0081] The operational amplifier circuit 20 of the sixth embodiment constitutes a 4-input / 4-output non-inverting input amplifier circuit and includes a first operational amplifier section 21, a second operational amplifier section 22, a third operational amplifier section 23, a fourth operational amplifier section 24, a resistor 105, and a Zener diode 501. In the above configuration, the first operational amplifier section 21 to the fourth operational amplifier section 24 constitute a non-inverting input amplifier circuit.
[0082] The first operational amplifier section 21 includes a resistor 101, a feedback resistor 103, a resistor 104, a capacitor 107, a capacitor 108, and a first operational amplifier 110.
[0083] One end of resistor 101 is connected to the inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 107. One end of the feedback resistor 103 is connected to the output terminal of the first operational amplifier 110, and the other end is connected to one end of resistor 101.
[0084] One end of resistor 104 is connected to the non-inverting input terminal of the first operational amplifier 110, and the other end is connected to the cathode terminal of Zener diode 501. One end of capacitor 107 is grounded, and the other end is connected to the other end of resistor 101.
[0085] One end of capacitor 108 is connected to the first non-inverting input terminal IN1, and the other end is connected to the other end of resistor 104. The first operational amplifier 110 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0086] Furthermore, the first operational amplifier 110 has an inverting input terminal connected to one end of resistor 101, a non-inverting input terminal connected to one end of resistor 104, and an output terminal connected to the output terminal OUT1 of the first operational amplifier section 21.
[0087] In the above configuration, the voltage at the connection point between resistor 105 and the cathode terminal of Zener diode 501 is set to the reference voltage VREF.
[0088] The second operational amplifier section 22 includes a resistor 201, a feedback resistor 203, a resistor 204, a capacitor 207, a capacitor 208, and a second operational amplifier 210.
[0089] One end of resistor 201 is connected to the inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 207. One end of the feedback resistor 203 is connected to the output terminal of the second operational amplifier 210, and the other end is connected to one end of resistor 201.
[0090] One end of resistor 204 is connected to the non-inverting input terminal of the second operational amplifier 210, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501. One end of capacitor 207 is grounded, and the other end is connected to the other end of resistor 201.
[0091] One end of capacitor 208 is connected to the second non-inverting input terminal IN2, and the other end is connected to the other end of resistor 204. The second operational amplifier 210 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0092] The third operational amplifier section 23 includes a resistor 301, a feedback resistor 303, a resistor 304, a capacitor 307, a capacitor 308, and a third operational amplifier 310.
[0093] One end of resistor 301 is connected to the inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 307. One end of the feedback resistor 303 is connected to the output terminal of the third operational amplifier 310, and the other end is connected to one end of resistor 301.
[0094] One end of resistor 304 is connected to the non-inverting input terminal of the third operational amplifier 310, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501. One end of capacitor 307 is grounded, and the other end is connected to the other end of resistor 301.
[0095] One end of capacitor 308 is connected to the third non-inverting input terminal IN3, and the other end is connected to the other end of resistor 304. The third operational amplifier 310 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0096] The fourth operational amplifier section 24 includes a resistor 401, a feedback resistor 403, a resistor 404, a capacitor 407, a capacitor 408, and a fourth operational amplifier 410.
[0097] One end of resistor 401 is connected to the inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 407. One end of the feedback resistor 403 is connected to the output terminal of the fourth operational amplifier 410, and the other end is connected to one end of resistor 401.
[0098] One end of resistor 404 is connected to the non-inverting input terminal of the fourth operational amplifier 410, and the other end is connected to the connection point between the other end of resistor 105 and the cathode terminal of Zener diode 501. One end of capacitor 407 is grounded, and the other end is connected to the other end of resistor 401.
[0099] One end of capacitor 408 is connected to the fourth non-inverting input terminal IN4, and the other end is connected to the other end of resistor 404. The fourth operational amplifier 410 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0100] Before providing a detailed description of the sixth embodiment, we will now explain the problems with conventional non-inverting input configuration operational amplifiers.
[0101] Figure 14 shows the configuration of a conventional non-inverting input operational amplifier circuit. Figure 14 shows the configuration of an operational amplifier circuit disclosed in Japanese Patent Application Publication No. 9-199955. The first output voltage VOUT1, which is the voltage at the first output terminal OUT1 when the input voltage VIN1 is applied to the input terminal IN1, is given by equations (4) and (5).
[0102]
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[0103]
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[0104] Furthermore, the reference voltage VREF when the voltage VIN1 is applied to the non-inverting input terminal IN1 is given by equations (5) and (6).
[0105]
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[0106] Figure 15 is an explanatory diagram of the simulation results for the circuit shown in Figure 14. Figure 15 shows an example of the characteristics (simulated values) when VIN1 = -18.5 dBV is input.
[0107] In Figure 15, the dotted line represents the output VOUT1 of the first output terminal OUT1, and the solid line represents the reference voltage VREF. When the non-inverting input terminal IN2 is left blank, the reference voltage VREF becomes equal to the voltage VOUT2 of the second output terminal OUT2, and this becomes the crosstalk from the non-inverting input terminal IN1 of the first operational amplifier 110 to the second operational amplifier 210.
[0108] Incidentally, one method for evaluating crosstalk performance involves applying a rated input to the non-inverting input terminal IN1 of the first operational amplifier 110, leaving the non-inverting input terminal IN2 of the second operational amplifier 210 blank, and observing the output difference between the output terminal OUT1 of the first operational amplifier 110 and the output terminal OUT2 of the second operational amplifier 210. Furthermore, the crosstalk frequency range may require frequencies not only around 1kHz but also below 100Hz.
[0109] As shown in Figure 15, the reference voltage VREF is frequency-dependent. The first-order low-pass filter, consisting of resistors 104, 105, 106, and capacitor 109, exhibits a downward-sloping characteristic of 6 dB / octave. Therefore, for example, if the required crosstalk performance is 60 dB, the requirement is met at 1 kHz but not at 100 Hz, which presents a problem.
[0110] Therefore, in this sixth embodiment, as in the first embodiment, a reference voltage generation circuit is configured using a Zener diode 501 that functions as a constant voltage element.
[0111] This allows the output impedance of the reference voltage generation circuit to be sufficiently reduced, so that the reference voltage VREF can be kept constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, the required crosstalk performance (e.g., 60 dB) can be met.
[0112] According to this sixth embodiment, in an operational amplifier circuit comprising multiple operational amplifier circuit sections, each having a non-inverting input operational amplifier that operates with a single power supply, crosstalk between operational amplifiers can be reduced.
[0113] [7] Seventh Embodiment Figure 16 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the seventh embodiment. In Figure 16, the same reference numerals are used for parts that are the same as those in the sixth embodiment in Figure 13.
[0114] The operational amplifier circuit 20A, like the operational amplifier circuit 20, constitutes a 4-input / 4-output non-inverting input amplifier circuit. The operational amplifier circuit 20A comprises a first operational amplifier section 21, a second operational amplifier section 22, a third operational amplifier section 23, a fourth operational amplifier section 24, and a constant voltage circuit CV1. In the above configuration, the constant voltage circuit CV1 functions as a reference voltage generation circuit.
[0115] Furthermore, the first operational amplifier section 21, the second operational amplifier section 22, the third operational amplifier section 23, and the fourth operational amplifier section 24 have the same configuration as in the sixth embodiment, so a detailed explanation thereof will be omitted.
[0116] The constant voltage circuit CV1 includes a Zener diode 501, a first transistor 502, a second transistor 503, a resistor 105, a resistor 504, and a resistor 505.
[0117] The anode terminal of the Zener diode 501 is grounded. The first transistor 502 has its emitter terminal connected to the cathode terminal of the Zener diode 501, and its collector terminal connected to the other end of the resistor 105.
[0118] The second transistor 503 has its collector terminal connected to the power supply Vcc, its base terminal connected to the collector terminal of the first transistor 502, and its emitter terminal connected to resistors 104, 204, 304, 404, and 504, serving as the output terminal for the reference voltage VREF.
[0119] Resistor 504 has one end connected to the emitter terminal of the second transistor 503 and the other end connected to the base terminal of the first transistor 502. Resistor 505 has one end connected to the connection point between resistor 504 and the base terminal of the first transistor 502, and the other end is grounded.
[0120] In the above configuration, since most of the emitter current of the second transistor 503 flows into the resistor 504, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1. The output impedance of the constant voltage circuit CV1, which serves as a reference voltage generation circuit, can be sufficiently reduced.
[0121] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, the required crosstalk performance (60 dB in the example above) can be met.
[0122] As described above, according to this seventh embodiment, similar to the sixth embodiment, in an operational amplifier circuit comprising multiple operational amplifier circuit sections, each having a non-inverting input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0123] [8] Eighth embodiment Figure 17 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the eighth embodiment. In Figure 17, the same reference numerals are used for parts that are the same as those in the sixth embodiment in Figure 13 and the seventh embodiment in Figure 16.
[0124] The operational amplifier circuit 20B, like the operational amplifier circuit 20, constitutes a 4-input / 4-output non-inverting input amplifier circuit. The operational amplifier circuit 20B comprises a first operational amplifier section 21, a second operational amplifier section 22, a third operational amplifier section 23, a fourth operational amplifier section 24, and a constant voltage circuit CV2. In the above configuration, the constant voltage circuit CV2 functions as a reference voltage generation circuit.
[0125] Furthermore, the first operational amplifier section 21, the second operational amplifier section 22, the third operational amplifier section 23, and the fourth operational amplifier section 24 have the same configuration as in the sixth embodiment, so a detailed explanation of them will be omitted.
[0126] The constant voltage circuit CV2 includes a Zener diode 501, a first transistor 502, a resistor 105, a resistor 106, and a capacitor 109. The anode terminal of the Zener diode 501 is grounded. The first transistor 502 has its emitter terminal connected to the cathode terminal of the Zener diode 501, and its collector terminal connected to the power supply Vcc.
[0127] Resistor 105 has one end connected to the power supply Vcc and the other end connected to the base terminal of the first transistor 502. Resistor 106 has one end connected to the connection point between the base terminal of the first transistor 502 and the other end of resistor 105, and the other end is grounded. Capacitor 109 is connected in parallel with resistor 106.
[0128] In the above configuration, since most of the emitter current of the first transistor 502 flows into the Zener diode 501, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1. The output impedance of the constant voltage circuit CV2, which serves as a reference voltage generation circuit, can be sufficiently reduced.
[0129] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation. As a result, similar to the embodiments described above, the required crosstalk performance (60 dB in the above example) can be met.
[0130] As described above, according to this eighth embodiment, similar to the sixth and seventh embodiments, in an operational amplifier circuit comprising multiple operational amplifier circuit sections, each having a non-inverting input operational amplifier operating on a single power supply, crosstalk between operational amplifiers can be reduced.
[0131] [9] Ninth Embodiment Figure 18 is an explanatory diagram illustrating an example of the configuration of an operational amplifier circuit according to the ninth embodiment. In Figure 18, the same reference numerals are used for parts that are the same as those in the sixth embodiment in Figure 13, the seventh embodiment in Figure 16, and the eighth embodiment in Figure 17.
[0132] The operational amplifier circuit 20C, like the operational amplifier circuit 20, constitutes a 4-input / 4-output non-inverting input amplifier circuit. The operational amplifier circuit 20C comprises a first operational amplifier section 21, a second operational amplifier section 22, a third operational amplifier section 23, a fourth operational amplifier section 24, and a constant voltage circuit CV3. In the above configuration, the constant voltage circuit CV3 functions as a reference voltage generation circuit.
[0133] Furthermore, the first operational amplifier section 21, the second operational amplifier section 22, the third operational amplifier section 23, and the fourth operational amplifier section 24 have the same configuration as in the sixth embodiment, so a detailed explanation of them will be omitted.
[0134] The constant voltage circuit CV3 comprises a first transistor 502, a resistor 105, a resistor 106, a capacitor 109, and a resistor 506. The first transistor 502 has its emitter terminal connected to one end of resistor 506 and its collector terminal connected to the power supply Vcc. Resistor 105 has one end connected to the power supply Vcc and the other end connected to the base terminal of the first transistor 502.
[0135] Resistor 106 has one end connected to the connection point between the base terminal of the first transistor 502 and the other end of resistor 105, and the other end is grounded. Capacitor 109 is connected in parallel with resistor 106. The other end of resistor 506 is grounded.
[0136] In the above configuration, the first transistor 502 and the resistor 506 constitute an emitter follower.
[0137] Since most of the emitter current from the first transistor 502 flows into resistor 506, the voltage of the reference voltage VREF is not affected by voltage fluctuations at the first non-inverting input terminal IN1.
[0138] This allows the reference voltage VREF to be effectively constant regardless of frequency in the frequency domain targeted for crosstalk performance evaluation.
[0139] As a result, similar to the embodiments described above, the required crosstalk performance (e.g., 60 dB) can be met across a wide frequency band.
[0140] As described above, according to this ninth embodiment, similar to the sixth, seventh, and eighth embodiments, it is possible to reduce crosstalk between operational amplifiers in an operational amplifier circuit that includes multiple operational amplifier circuit sections, each having a non-inverting input operational amplifier that operates on a single power supply.
[0141]
[10] Tenth embodiment Figure 19 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the tenth embodiment. In Figure 19, the same reference numerals are used for parts that are the same as those in the sixth embodiment in Figure 13, the seventh embodiment in Figure 16, the eighth embodiment in Figure 17, and the ninth embodiment in Figure 18.
[0142] The operational amplifier circuit 20D, like the operational amplifier circuit 20, constitutes a 4-input / 4-output non-inverting input amplifier circuit. The operational amplifier circuit 20D comprises a first operational amplifier section 21, a second operational amplifier section 22, a third operational amplifier section 23, a fourth operational amplifier section 24, and a constant voltage circuit CV4.
[0143] In the above configuration, the constant voltage circuit CV4 functions as a reference voltage generation circuit. Furthermore, the first operational amplifier section 21, the second operational amplifier section 22, the third operational amplifier section 23, and the fourth operational amplifier section 24 have the same configuration as in the sixth embodiment, so a detailed explanation of them will be omitted.
[0144] The constant voltage circuit CV4 has the same function as the constant voltage circuit CV3 of the ninth embodiment, and instead of an emitter follower circuit composed of the first transistor 502 and resistor 506, it is equipped with an operational amplifier 510. Resistor 105 has one end connected to the power supply Vcc and the other end connected to one end of resistor 106.
[0145] Resistor 106 has one end connected to the other end of resistor 105, and the other end is grounded. The non-inverting input terminal of the op-amp 510 is connected to the connection point between resistors 105 and 106, and its output terminal is connected to the inverting input terminal. Capacitor 109 is connected in parallel with resistor 106.
[0146] In the above configuration, the operational amplifier 510 has a low output impedance, similar to the emitter follower in the ninth embodiment.
[0147] The reference voltage VREF can be effectively kept constant regardless of frequency within the frequency band targeted for crosstalk performance evaluation. As a result, the required crosstalk performance can be fully met, similar to the embodiments described above. As described above, according to this tenth embodiment, similar to the sixth, seventh, eighth, and ninth embodiments, it is possible to reduce crosstalk between operational amplifiers in an operational amplifier circuit that includes multiple operational amplifier circuit sections, each having a non-inverting input operational amplifier that operates on a single power supply.
[0148]
[11] Eleventh Embodiment Figure 20 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the 11th embodiment. The operational amplifier circuit 30 constitutes a 4-input / 4-output differential input amplifier circuit and includes a first operational amplifier section 31, a second operational amplifier section 32, a third operational amplifier section 33, and a fourth operational amplifier section 34.
[0149] In the above configuration, the first operational amplifier section 31 to the fourth operational amplifier section 34 constitute a differential input amplifier circuit.
[0150] The first operational amplifier section 31 includes resistors 101, 102, feedback resistor 103, 104, 105, 106, capacitors 107, 108, 109, and the first operational amplifier 110. In the above configuration, resistors 101 and 102 function as input resistors, and capacitors 107 and 108 function as input capacitors. One end of resistor 101 is connected to the inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 107.
[0151] One end of resistor 102 is connected to the non-inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 108. One end of the feedback resistor 103 is connected to the output terminal of the first operational amplifier 110, and the other end is connected to one end of resistor 101.
[0152] One end of resistor 104 is connected to the non-inverting input terminal of the first operational amplifier 110. One end of resistor 105 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 104. One end of resistor 106 is connected to the connection point between resistors 104 and 105, and the other end is grounded.
[0153] One end of capacitor 107 is connected to the first inverting input terminal IN1-, and the other end is connected to the other end of resistor 101. One end of capacitor 108 is connected to the first non-inverting input terminal IN1+, and the other end is connected to the other end of resistor 102.
[0154] Capacitor 109 is connected in parallel with resistor 106. The first operational amplifier 110 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0155] In the above configuration, resistors 105 and 106 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF1 to the non-inverting input terminal of the first operational amplifier 110 via resistor 104.
[0156] Furthermore, resistors 104, 105, 106, and capacitor 109 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF1 from being input to the first operational amplifier 110.
[0157] The second operational amplifier section 32 includes resistors 201, 202, feedback resistors 203, 204, 205, 206, capacitors 207, 208, 209, and a second operational amplifier 210. In the above configuration, resistors 201 and 202 function as input resistors, and capacitors 207 and 208 function as input capacitors. One end of resistor 201 is connected to the inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 207.
[0158] One end of resistor 202 is connected to the non-inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 208. One end of the feedback resistor 203 is connected to the output terminal of the second operational amplifier 210, and the other end is connected to one end of resistor 201.
[0159] One end of resistor 204 is connected to the non-inverting input terminal of the second operational amplifier 210. One end of resistor 205 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 204. One end of resistor 206 is connected to the connection point between resistors 204 and 205, and the other end is grounded.
[0160] One end of capacitor 207 is connected to the second inverting input terminal IN2-, and the other end is connected to the other end of resistor 201. One end of capacitor 208 is connected to the second non-inverting input terminal IN2+, and the other end is connected to the other end of resistor 202.
[0161] Capacitor 209 is connected in parallel with resistor 206. The second operational amplifier 210 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0162] In the above configuration, resistors 205 and 206 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF2 to the non-inverting input terminal of the second operational amplifier 210 via resistor 204.
[0163] Furthermore, resistors 204, 205, 206, and capacitor 209 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF2 from being input to the second operational amplifier 210.
[0164] The third operational amplifier section 33 includes a resistor 301, a resistor 302, a feedback resistor 303, a resistor 304, a resistor 305, a resistor 306, a capacitor 307, a capacitor 308, a capacitor 309, and a third operational amplifier 310. In the above configuration, resistors 301 and 302 function as input resistors, and capacitors 307 and 308 function as input capacitors. One end of resistor 301 is connected to the inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 307.
[0165] One end of resistor 302 is connected to the non-inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 308. One end of the feedback resistor 303 is connected to the output terminal of the third operational amplifier 310, and the other end is connected to one end of resistor 301.
[0166] One end of resistor 304 is connected to the non-inverting input terminal of the third operational amplifier 310. One end of resistor 305 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 304. One end of resistor 306 is connected to the connection point between resistors 304 and 305, and the other end is grounded.
[0167] One end of capacitor 307 is connected to the third inverting input terminal IN3-, and the other end is connected to the other end of resistor 301. One end of capacitor 308 is connected to the third non-inverting input terminal IN3+, and the other end is connected to the other end of resistor 302.
[0168] Capacitor 309 is connected in parallel with resistor 306. The third operational amplifier 310 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0169] In the above configuration, resistors 305 and 306 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF3 to the non-inverting input terminal of the third operational amplifier 310 via resistor 304.
[0170] Furthermore, resistors 304, 305, 306, and capacitor 309 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF3 from being input to the third operational amplifier 310.
[0171] The fourth operational amplifier section 34 includes a resistor 401, a resistor 402, a feedback resistor 403, a resistor 404, a resistor 405, a resistor 406, a capacitor 407, a capacitor 408, a capacitor 409, and a fourth operational amplifier 410. In the above configuration, resistors 401 and 402 function as input resistors, and capacitors 407 and 408 function as input capacitors. One end of resistor 401 is connected to the inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 407.
[0172] One end of resistor 402 is connected to the non-inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 408. One end of the feedback resistor 403 is connected to the output terminal of the fourth operational amplifier 410, and the other end is connected to one end of resistor 401.
[0173] One end of resistor 404 is connected to the non-inverting input terminal of the fourth operational amplifier 410. One end of resistor 405 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 404. One end of resistor 406 is connected to the connection point between resistors 404 and 405, and the other end is grounded.
[0174] One end of capacitor 407 is connected to the fourth inverting input terminal IN4-, and the other end is connected to the other end of resistor 401. One end of capacitor 408 is connected to the fourth non-inverting input terminal IN4+, and the other end is connected to the other end of resistor 402.
[0175] Capacitor 409 is connected in parallel with resistor 406. The fourth operational amplifier 410 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0176] In the above configuration, resistors 405 and 406 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF4 to the non-inverting input terminal of the fourth operational amplifier 410 via resistor 404.
[0177] Furthermore, resistors 404, 405, 406, and capacitor 409 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF4 from being input to the fourth operational amplifier 410.
[0178] Figure 21 is an explanatory diagram of the frequency characteristics of the reference voltage VREF1 when a predetermined voltage is applied. Figure 21 shows an example of the frequency characteristics (simulated values) when -18.5 dBV (θ=0 deg) is applied to the first non-inverting input terminal IN1+ and -18.5 dBV (θ=180 deg) is applied to the first inverting input terminal IN1-. Here, θ is the phase of voltage VIN1+ and voltage VIN1-.
[0179] The dotted line represents the output voltage VOUT1 of the output terminal OUT1 of the first operational amplifier 110, and the solid line represents the voltage of the reference voltage VREF1. In the above configuration, the reference voltage VREF1 and reference voltages VREF2 to VREF4 are uncorrelated with each other, and reference voltages VREF2 to VREF4 are not affected by reference voltage VREF1.
[0180] Therefore, for example, even if there is an input of -18.5 dBV (θ=0 deg) at the first non-inverting input terminal IN1+ of the first operational amplifier 110, the input signal at the first non-inverting input terminal IN1+ will not be output to the reference voltages VREF2~VREF4. The output of the reference voltages VREF2~VREF4 from the first non-inverting input terminal IN1+ will remain at -∞.
[0181] For similar reasons, it can be seen that no crosstalk occurs between the differential inputs of the first operational amplifier 110, the second operational amplifier 210, the third operational amplifier 310, and the fourth operational amplifier 410. As described above, according to the 11th embodiment, each channel (e.g., audio channel) corresponding to the first operational amplifier 110, the second operational amplifier 210, the third operational amplifier 310, or the fourth operational amplifier 410 is isolated, and the corresponding reference voltages VREF1 to VREF4 are uncorrelated with respect to each other, so no crosstalk occurs.
[0182]
[12] Twelfth Embodiment While the 11th embodiment described above described an operational amplifier circuit with differential inputs, this 12th embodiment is an embodiment of an operational amplifier circuit with non-inverting inputs. Figure 22 is an explanatory diagram of an example configuration of an operational amplifier circuit according to the twelfth embodiment. In Figure 22, parts similar to those in the sixth embodiment in Figure 13 are denoted by the same reference numerals.
[0183] The operational amplifier circuit 30A of the twelfth embodiment constitutes a 4-input / 4-output non-inverting input amplifier circuit and includes a first operational amplifier section 41, a second operational amplifier section 42, a third operational amplifier section 43, and a fourth operational amplifier section 44. In the above configuration, the first operational amplifier section 41 to the fourth operational amplifier section 44 constitute a non-inverting input amplifier circuit.
[0184] The first operational amplifier section 41 includes a resistor 101, a feedback resistor 103, a resistor 104, a resistor 105, a resistor 106, a capacitor 107, a capacitor 108, a capacitor 109, and a first operational amplifier 110. One end of resistor 101 is connected to the inverting input terminal of the first operational amplifier 110, and the other end is connected to one end of capacitor 107.
[0185] One end of the feedback resistor 103 is connected to the output terminal of the first operational amplifier 110, and the other end is connected to one end of resistor 101. One end of resistor 104 is connected to the non-inverting input terminal of the first operational amplifier 110. One end of resistor 105 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 104.
[0186] One end of resistor 106 is connected to the connection point between resistors 104 and 105, and the other end is grounded. One end of capacitor 107 is grounded, and the other end is connected to the other end of resistor 101.
[0187] One end of capacitor 108 is connected to the first non-inverting input terminal IN1, and the other end is connected to the other end of resistor 104. Capacitor 109 is connected in parallel with resistor 106. The first operational amplifier 110 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0188] In the above configuration, resistors 105 and 106 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF1 to the non-inverting input terminal of the first operational amplifier 110 via resistor 104.
[0189] Furthermore, resistors 104, 105, 106, and capacitor 109 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF1 from being input to the first operational amplifier 110.
[0190] The second operational amplifier section 42 includes a resistor 201, a feedback resistor 203, a resistor 204, a resistor 205, a resistor 206, a capacitor 207, a capacitor 208, a capacitor 209, and a second operational amplifier 210. One end of resistor 201 is connected to the inverting input terminal of the second operational amplifier 210, and the other end is connected to one end of capacitor 207.
[0191] One end of the feedback resistor 203 is connected to the output terminal of the second operational amplifier 210, and the other end is connected to one end of resistor 201. One end of resistor 204 is connected to the non-inverting input terminal of the second operational amplifier 210. One end of resistor 205 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 204.
[0192] One end of resistor 206 is connected to the connection point between resistors 204 and 205, and the other end is grounded. One end of capacitor 207 is grounded, and the other end is connected to the other end of resistor 201.
[0193] One end of capacitor 208 is connected to the second non-inverting input terminal IN2, and the other end is connected to the other end of resistor 204. Capacitor 209 is connected in parallel with resistor 206. The second operational amplifier 210 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0194] In the above configuration, resistors 205 and 206 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF2 to the non-inverting input terminal of the second operational amplifier 210 via resistor 204.
[0195] Furthermore, resistors 204, 205, 206, and capacitor 209 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF2 from being input to the second operational amplifier 210.
[0196] The third operational amplifier section 43 includes a resistor 301, a feedback resistor 303, a resistor 304, a resistor 305, a resistor 306, a capacitor 307, a capacitor 308, a capacitor 309, and a third operational amplifier 310. One end of resistor 301 is connected to the inverting input terminal of the third operational amplifier 310, and the other end is connected to one end of capacitor 307.
[0197] One end of the feedback resistor 303 is connected to the output terminal of the third operational amplifier 310, and the other end is connected to one end of resistor 301. One end of resistor 304 is connected to the non-inverting input terminal of the third operational amplifier 310. One end of resistor 305 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 304.
[0198] One end of resistor 306 is connected to the connection point between resistors 304 and 305, and the other end is grounded. One end of capacitor 307 is grounded, and the other end is connected to the other end of resistor 301.
[0199] One end of capacitor 308 is connected to the third inverting input terminal IN3, and the other end is connected to the other end of resistor 304. Capacitor 309 is connected in parallel with resistor 306. The third operational amplifier 310 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0200] In the above configuration, resistors 305 and 306 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF3 to the non-inverting input terminal of the third operational amplifier 310 via resistor 304.
[0201] Furthermore, resistors 304, 305, 306, and capacitor 309 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF3 from being input to the third operational amplifier 310.
[0202] The fourth operational amplifier section 44 includes a resistor 401, a feedback resistor 403, a resistor 404, a resistor 405, a resistor 406, a capacitor 407, a capacitor 408, a capacitor 409, and a fourth operational amplifier 410. One end of resistor 401 is connected to the inverting input terminal of the fourth operational amplifier 410, and the other end is connected to one end of capacitor 407.
[0203] One end of the feedback resistor 403 is connected to the output terminal of the fourth operational amplifier 410, and the other end is connected to one end of resistor 401. One end of resistor 404 is connected to the non-inverting input terminal of the fourth operational amplifier 410. One end of resistor 405 is connected to the power supply Vcc, and the other end is connected to the other end of resistor 404.
[0204] One end of resistor 406 is connected to the connection point between resistors 404 and 405, and the other end is grounded. One end of capacitor 407 is grounded, and the other end is connected to the other end of resistor 401.
[0205] One end of capacitor 408 is connected to the fourth non-inverting input terminal IN4, and the other end is connected to the other end of resistor 404. Capacitor 409 is connected in parallel with resistor 406. The fourth operational amplifier 410 has one power supply terminal connected to the power supply Vcc and the other power supply terminal connected to ground.
[0206] In the above configuration, resistors 405 and 406 function as voltage divider resistors, dividing the voltage of the power supply Vcc and outputting it as a reference voltage VREF4 to the non-inverting input terminal of the fourth operational amplifier 410 via resistor 404.
[0207] Furthermore, resistors 404, 405, 406, and capacitor 409 function as a first-order low-pass filter, preventing high-frequency noise from the reference voltage VREF4 from being input to the fourth operational amplifier 410.
[0208] In the above configuration, as in the 11th embodiment, the reference voltage VREF1 and reference voltages VREF2 to VREF4 are uncorrelated with each other, and reference voltages VREF2 to VREF4 are not affected by reference voltage VREF1.
[0209] Therefore, for example, even if there is an input of -18.5 dBV at the first non-inverting input terminal IN1 of the first operational amplifier 110, the input signal at the first non-inverting input terminal IN1 will not be output to the reference voltages VREF2 to VREF4. The output of the reference voltages VREF2 to VREF4 from the first non-inverting input terminal IN1 will remain at -∞.
[0210] For similar reasons, no crosstalk occurs between the non-inverting inputs of the first operational amplifier 110, the second operational amplifier 210, the third operational amplifier 310, and the fourth operational amplifier 410. As described above, according to the 12th embodiment, each channel (e.g., audio channel) corresponding to the first operational amplifier 110, the second operational amplifier 210, the third operational amplifier 310, or the fourth operational amplifier 410 is isolated, and the corresponding reference voltages VREF1 to VREF4 are uncorrelated with respect to each other, so no crosstalk occurs.
[0211] As described above, according to each embodiment, in an operational amplifier circuit comprising multiple operational amplifier sections, each having an operational amplifier driven by a single power supply, it becomes possible to reduce crosstalk between operational amplifiers and perform signal amplification.
[0212] Although the application examples of the operational amplifier circuit have not been described, for example, a differential output microphone is connected to the input terminals of a differential input operational amplifier, and a single-ended output microphone is connected to the input terminals of a non-inverting input operational amplifier. Therefore, it is possible to suppress distortion due to crosstalk of the output signals of each microphone and perform signal transmission with high channel separation.
[0213] Although some embodiments of the present invention have been described, these embodiments are illustrative and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.
Description of Reference Numerals
[0214] CV1 to CV4 Constant voltage circuits 10, 10A to 10D Operational amplifier circuits 11, 21, 31, 41 First operational amplifier sections 12, 22, 32, 42 Second operational amplifier sections 13, 23, 33, 43 Third operational amplifier sections 14, 24, 34, 44 Fourth operational amplifier sections 20, 20A to 20D Operational amplifier circuits 101, 102 Resistors 103 Feedback resistor 104 to 106 Resistors 107, 108 Capacitors 109 Capacitor 110 First operational amplifier 201, 202 Resistors 203 Feedback resistor 204 to 206 Resistors 207, 208 Capacitors 209 Capacitor 210 Second operational amplifier 301, 302 resistors 303 Feedback resistor 304~306 Resistors 307, 308 Capacitors 309 Capacitor 310 Third operational amplifier 401, 402 resistors 403 Feedback resistor 404~406 Resistors 407, 408 Capacitors 409 Capacitor 410 4th operational amplifier 501 Zener Diode 502 First Transistor 503 Second Transistor 504~506 Resistors 510 Op-amp OUT1~OUT4 Output terminals Vcc power supply VREF, VREF1~VREF4 Reference Voltage
Claims
1. A reference voltage generation circuit that is connected to a single power supply and generates and outputs a reference voltage signal, A plurality of operational amplifier circuits, each having an operational amplifier that operates on a single power supply, Equipped with, The output impedance of the reference voltage generation circuit is set such that the voltage fluctuation amount of the reference voltage signal is less than or equal to a predetermined value. Operational amplifier circuit.
2. The aforementioned reference voltage generation circuit includes a Zener diode connected to ground in a reverse bias state. The operational amplifier circuit according to claim 1.
3. The aforementioned reference voltage generation circuit includes a voltage divider circuit that divides the voltage of the single power supply, The output voltage of the voltage divider circuit is input to a control terminal, and the emitter follower circuit generates the reference voltage signal. The operational amplifier circuit according to claim 1.
4. The aforementioned reference voltage generation circuit includes a voltage divider circuit that divides the voltage of the single power supply, The output voltage of the voltage divider circuit is input to the input terminal of an operational amplifier that generates the reference voltage signal, The operational amplifier circuit according to claim 1, comprising:
5. The aforementioned operational amplifier is configured as a differential input operational amplifier. The operational amplifier circuit according to claim 1.
6. The aforementioned operational amplifier is configured as a non-inverting input operational amplifier. The operational amplifier circuit according to claim 1.
7. The system includes a low-pass filter that removes high-frequency components from the output of the reference voltage generation circuit and supplies it to the operational amplifier. The operational amplifier circuit according to claim 1.
8. Multiple reference voltage generation circuits connected to a single power supply generate and output a reference voltage signal, A plurality of operational amplifier circuits, each having an operational amplifier that operates on a single power supply, Equipped with, The aforementioned multiple reference voltage generation circuits are each connected to the non-inverting input of the operational amplifier circuit section, which is paired one-to-one. Operational amplifier circuit.
9. The aforementioned reference voltage generation circuit includes a voltage divider circuit that divides the voltage of the single power supply, A low-pass filter that removes a predetermined high-frequency component from the output voltage of the voltage divider circuit, The operational amplifier circuit according to claim 8, comprising:
10. The aforementioned operational amplifier is configured as a differential input operational amplifier. The operational amplifier circuit according to claim 8.
11. The aforementioned operational amplifier is configured as a non-inverting input operational amplifier. The operational amplifier circuit according to claim 8.