Non-inverting amplifier circuit

Abstract

The present invention provides a non-inverting amplifier circuit capable of sufficiently improving low frequency characteristics.　A non-inverting amplifier circuit 1A performs non-inverting amplification of an input signal SINA input to a signal input part ISA by a gain of 1, and outputs the resultant as an output signal SOUTA from a signal output part OSA. The non-inverting amplifier circuit 1A is provided with operational amplifiers OP1A, OP2A. The operational amplifier OP1A is configured so as to have an inverting input terminal connected to the signal input part ISA, an output terminal connected to the signal output part OSA, and an inverting input terminal connected to the output terminal via a resistor R1A. The operational amplifier OP2A is configured so as to have a non-inverting input terminal connected to the output terminal of the operational amplifier OP1A, an inverting input terminal connected to the signal input part ISA, and an output terminal connected to the inverting input terminal of the operational amplifier OP1A via a resistor R2A.

Description

Non-inverting amplifier circuit

[0001] The present invention relates to a non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a predetermined gain and outputs the amplified signal as an output signal from a signal output section.

[0002] Known examples of this type of non-inverting amplifier circuit include the one disclosed in the following non-patent document: This non-inverting amplifier circuit is configured by connecting the inverting input terminal of an operational amplifier to the output terminal, and operates as a so-called unity gain buffer, non-invertingly amplifying an input signal input to the non-inverting input terminal with a gain of 1 and outputting it as an output signal from the output terminal.

[0003] Another known non-inverting amplifier circuit that also operates as a unity gain buffer is the non-inverting amplifier circuit 1X shown in FIG. 9. This non-inverting amplifier circuit 1X includes an operational amplifier OP1X, the inverting input terminal of which is connected to the output terminal via resistor R1X and to the non-inverting input terminal via resistor R2X. In this non-inverting amplifier circuit 1X, an input signal SINX input to the non-inverting input terminal of the operational amplifier OP1X is non-inverting-amplified and output from the output terminal as an output signal SOUTX. In this case, when the resistance value of resistor R1X is R1X, the resistance value of resistor R2X is R2X, the voltage value of the input signal SINX is VINX, and the voltage value of the output signal SOUTX is VOUTX, the non-inverting amplifier circuit 1X operates to satisfy the following relationship: VOUTX = VINX

[0004] Another known non-inverting amplifier circuit is the one described in the following non-patent document. As shown in FIG. 10 , this non-inverting amplifier circuit 1Y includes an operational amplifier OP1Y, whose inverting input terminal is connected to an output terminal via a resistor R1Y and to ground via a resistor R2Y. The non-inverting amplifier circuit 1Y non-inverts and amplifies an input signal SINY input to the non-inverting input terminal of the operational amplifier OP1Y, and outputs the amplified signal as an output signal SOUTY from the output terminal. In this case, the non-inverting amplifier circuit 1Y operates to satisfy the following relationship: VOUTY = ((R1Y + R2Y) / R2Y) × VINY, where R1Y is the resistance of the resistor R1Y, R2Y is the resistance of the resistor R2Y, VINY is the voltage of the input signal SINY, and VOUTY is the voltage of the output signal SOUTY.

[0005] JP 2017-20963 A (pages 6-16, Figure 1)

[0006] Hideo Tsunoda, Practical Operational Amplifier Circuits, Tokyo Denki University Press, February 1997

[0007] However, while the above-mentioned conventional non-inverting amplifier circuits can easily be configured to have excellent high-frequency characteristics, they have the problem of difficulty in improving low-frequency characteristics (DC characteristics) such as reducing the offset voltage and so-called 1 / f noise that occur between the inverting and non-inverting input terminals of the operational amplifier. Specifically, as shown in Figure 9, in the above-mentioned non-inverting amplifier circuit 1X, when an offset voltage SOF (voltage value VOF) occurs between the inverting and non-inverting input terminals of the operational amplifier OP1X, the voltage value VOUTX of the output signal SOUTX will include the voltage VOF in the voltage VINX, as follows: VOUTX = VINX + VOF

[0008] 10, in the non-inverting amplifier circuit 1Y, when an offset voltage SOF (voltage value VOF) occurs between the inverting input terminal and the non-inverting input terminal of the operational amplifier OP1Y, the voltage value VOUTY of the output signal SOUTY includes the voltage VOF in the voltage VINY, as follows: VOUTY=((R1Y+R2Y) / R2Y)×(VINY+VOF).

[0009] The present invention has been made in view of the above-mentioned problems, and has as its main object to provide a non-inverting amplifier circuit that can sufficiently improve low-frequency characteristics.

[0010] In order to achieve the above object, a non-inverting amplifier circuit according to the present invention is a non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a gain of 1 and outputs the amplified signal as an output signal from a signal output section, and includes a first-A operational amplifier and a second-A operational amplifier, wherein the first-A operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to an output terminal via a first-A resistor, and an output terminal connected to the signal output section, and the second-A operational amplifier has a non-inverting input terminal connected to the output terminal of the first-A operational amplifier, an inverting input terminal connected to the signal input section, and an output terminal connected to the inverting input terminal of the first-A operational amplifier via a second-A resistor.

[0011] With this non-inverting amplifier circuit, even if an offset voltage or 1 / f noise occurs in the first A operational amplifier, the offset voltage or 1 / f noise can be sufficiently removed and output as an output signal.

[0012] Furthermore, in order to achieve the above object, a non-inverting amplifier circuit according to the present invention is a non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a gain of 1 and outputs the amplified signal as an output signal from a signal output section, and includes a first A operational amplifier and a second A operational amplifier, wherein the first A operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to an output terminal via a first A resistor, and the output terminal connected to the signal output section, and the second A operational amplifier has a non-inverting input terminal connected to the output terminal of the first A operational amplifier, The inverting input terminal is connected to the signal input section via a 3A resistor and to the output terminal via a 1A capacitor, and the output terminal is connected to the inverting input terminal of the first A operational amplifier via a 2A resistor, and the 2A resistor is configured as a series circuit of a 4A resistor connected to the inverting input terminal of the first A operational amplifier and a 5A resistor connected to the output terminal of the second A operational amplifier, and the connection point of the 4A resistor and the 5A resistor and the non-inverting input terminal of the first A operational amplifier are connected by a 2A capacitor.

[0013] This non-inverting amplifier circuit, which combines the first A operational amplifier and the second A operational amplifier, can sufficiently remove offset voltage and 1 / f noise from the first A operational amplifier to produce an output signal. Furthermore, this non-inverting amplifier circuit can sufficiently improve low-frequency characteristics (DC characteristics) while maintaining the good high-frequency characteristics of the first operational amplifier A.

[0014] Furthermore, in order to achieve the above object, a non-inverting amplifier circuit according to the present invention is a non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a predetermined gain and outputs the result as an output signal from a signal output section, and includes a first-B operational amplifier and a second-B operational amplifier, wherein the first-B operational amplifier has an inverting input terminal connected to an output terminal via a first-B resistor and to an intermediate potential via a second-B resistor, and the output terminal connected to the signal output section, and the second-B operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to the inverting input terminal of the first-B operational amplifier, and the output terminal connected to the non-inverting input terminal of the first-B operational amplifier.

[0015] According to this non-inverting amplifier circuit, even if an offset voltage or 1 / f noise occurs in the first B operational amplifier, the offset voltage or 1 / f noise can be sufficiently removed and output as an output signal.

[0016] Furthermore, in order to achieve the above object, a non-inverting amplifier circuit according to the present invention is a non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a predetermined gain and outputs the result as an output signal from a signal output section, and includes a first-B operational amplifier and a second-B operational amplifier, wherein the first-B operational amplifier has a non-inverting input terminal connected to the signal input section via a first-B capacitor, an inverting input terminal connected to an output terminal via a first-B resistor and to an intermediate potential via a second-B resistor, and an output terminal connected to the signal output section, and the second-B operational amplifier has a non-inverting input terminal connected to the signal input section via a third-B resistor, an inverting input terminal connected to the inverting input terminal of the first-B operational amplifier via a fourth-B resistor and to the output terminal via the second-B capacitor, and an output terminal connected to the non-inverting input terminal of the first-B operational amplifier via a fifth-B resistor.

[0017] This non-inverting amplifier circuit, which combines the first-B operational amplifier and the second-B operational amplifier, can sufficiently remove offset voltage and 1 / f noise from the first-B operational amplifier, thereby outputting the output signal. Furthermore, this non-inverting amplifier circuit can sufficiently improve the low-frequency characteristics (DC characteristics) while maintaining the good high-frequency characteristics of the first-B operational amplifier.

[0018] According to the non-inverting amplifier circuit of the present invention, even if an offset voltage or 1 / f noise occurs in the first A operational amplifier or the first B operational amplifier, the offset voltage or 1 / f noise can be sufficiently removed and output as an output signal.

[0019] 1 is a circuit diagram of a non-inverting amplifier circuit 1A. FIG. 2 is an equivalent circuit diagram of the non-inverting amplifier circuit 1A when the input signal SINA is a high-frequency signal. FIG. 3 is a frequency characteristics diagram showing the frequency characteristics of noise (1 / f noise) included in the output signal output from the conventional non-inverting amplifier circuit described in the above publication. FIG. 4 is a frequency characteristics diagram showing the frequency characteristics of noise (1 / f noise) included in the output signal SOUTA output from the non-inverting amplifier circuit 1A. FIG. 5 is a circuit diagram of a non-inverting amplifier circuit 1B. FIG. 6 is an equivalent circuit diagram of an inverting amplifier circuit 1B when the input signal SINB is a high-frequency signal. FIG. 7 is a frequency characteristics diagram showing the frequency characteristics of noise (1 / f noise) included in the output signal SOUTY output from a conventional non-inverting amplifier circuit 1Y. FIG. 8 is a frequency characteristics diagram showing the frequency characteristics of noise (1 / f noise) included in the output signal SOUTAB output from the non-inverting amplifier circuit 1B. FIG. 9 is a circuit diagram of a conventional non-inverting amplifier circuit 1X. FIG. 10 is a circuit diagram of a conventional non-inverting amplifier circuit 1Y.

[0020] Hereinafter, embodiments of a non-inverting amplifier circuit will be described with reference to the accompanying drawings.

[0021] (First Embodiment) The non-inverting amplifier circuit 1A shown in FIG. 1 is a so-called unity gain buffer, and is configured to function as a non-inverting amplifier circuit that non-inverts and amplifies an input signal SINA input via a signal input section ISA with a gain of 1 and outputs the amplified signal as an output signal SOUTA from a signal output section OSA.

[0022] Specifically, the non-inverting amplifier circuit 1A includes an operational amplifier OP1A with good high-frequency characteristics (e.g., good wideband characteristics) that functions as a first operational amplifier A, and an operational amplifier OP2A with good low-frequency characteristics that functions as a second operational amplifier A. Each of the operational amplifiers OP1A and OP2A operates using a power supply voltage that is a positive voltage and a negative voltage that have equal absolute values ​​relative to the ground potential, which serves as an intermediate potential.

[0023] In this case, the operational amplifier OP1A has a non-inverting input terminal (first A non-inverting input terminal) connected to the signal input section ISA, an inverting input terminal (first A inverting input terminal) connected to the output terminal (first A output terminal) via a resistor R1A (first A resistor), and an output terminal connected to the signal output section OSA. The operational amplifier OP2A has a non-inverting input terminal (second A non-inverting input terminal) connected to the output terminal of the operational amplifier OP1A, an inverting input terminal (second A inverting input terminal) connected to the signal input section ISA via a resistor R3A (third A resistor) and to the output terminal via a capacitor C1A (first A capacitor), and an output terminal (second A output terminal) connected to the inverting input terminal of the operational amplifier OP1A via a resistor R2A (second A resistor). In this case, resistor R2A is composed of a series circuit of resistor R4A (fourth A resistor) connected to the inverting input terminal of operational amplifier OP1A and resistor R5A (fifth A resistor) connected to the output terminal of operational amplifier OP2A, and the connection point P1 between resistors R4A and R5A and the non-inverting input terminal of operational amplifier OP1A are connected by capacitor C2A (second A capacitor).

[0024] Next, the operation of this non-inverting amplifier circuit 1A will be described.

[0025] First, we will explain the operation of the non-inverting amplifier circuit 1A when the input signal SINA is a DC signal or a signal with a sufficiently low frequency (hereinafter, both will be collectively referred to as "DC signals"). When the input signal SINA is a DC signal, the impedance of capacitors C1A and C2A becomes extremely large and the resistance value of resistor R3A is negligible. Therefore, in the non-inverting amplifier circuit 1A, the inverting input terminal of operational amplifier OP2A is equivalently connected directly to signal input section ISA and is open to the output terminal, and connection point P1 is open to the non-inverting input terminal of operational amplifier OP1A.

[0026] Therefore, when the input signal SINA is a DC signal, the non-inverting amplifier circuit 1A is represented by the circuit configuration shown in Figure 2. Therefore, in the non-inverting amplifier circuit 1A, the operational amplifier OP1A has a non-inverting input terminal connected to the signal input section ISA, an inverting input terminal connected to the output terminal via a resistor R1A, and an output terminal connected to a signal output section OSA. Furthermore, the operational amplifier OP2A has a non-inverting input terminal connected to the output terminal of the operational amplifier OP1A, an inverting input terminal connected directly to the signal input section ISA, and an output terminal connected to the inverting input terminal of the operational amplifier OP1A via a resistor R2A.

[0027] In this circuit configuration, when the open gain of operational amplifier OP2A is A, the resistance value of resistor R1A is R1A, the resistance value of resistor R2A (the series circuit of resistors R4A and R5A) is R2A, the voltage value of input signal SINA is VINA, the voltage value of output signal SOUTA is VOUTA, and the voltage value of offset voltage SOF occurring between the inverting input terminal and non-inverting input terminal of operational amplifier OP1A is VOF, the following equation (1) can be derived: VINA + VOF = (R1 × A / (R1 + R2)) × (VOUTA - VINA)) + (R2 / (R1 + R2)) × VOUTA ... (1)

[0028] Therefore, the voltage value VOUTA of the output signal SOUTA is expressed by the following equation (2): VOUTA=((1+(R1+R2) / (R1×A)) / (1+R2 / (R1×A)))×VINA+((1+R1 / R2) / (1+(R1×A) / R2))×VOF (2)

[0029] If the open gain A of the operational amplifier OP2A is sufficiently large, the voltage value VOUTA of the output signal SOUTA is expressed by the following equation (3): VOUTA=VINA (3)

[0030] In other words, in this non-inverting amplifier circuit 1A, even if an offset voltage S or 1 / f noise occurs in the operational amplifier OP1A, a unity gain buffer can be configured that can output an output signal S that does not include the offset voltage S or 1 / f noise.

[0031] As shown in Figure 3, the output signal output from the conventional non-inverting amplifier circuit described in the above publication has a high level of noise that is considered to be 1 / f noise superimposed in the low frequency range including DC signals. In contrast, as shown in Figure 4, the output signal SOUTA output from this non-inverting amplifier circuit 1A has sufficiently reduced noise that is considered to be 1 / f noise in the low frequency range including DC signals.

[0032] Next, with reference to FIG. 1, the operation of the non-inverting amplifier circuit 1A when the input signal SINA is a high-frequency signal will be described.

[0033] When the input signal SINA is a high-frequency signal, the impedances of capacitors C1A and C2A are sufficiently small. Therefore, in the non-inverting amplifier circuit 1A, junction P1 and the non-inverting input terminal of operational amplifier OP1A are short-circuited, causing operational amplifier OP2A to malfunction. Specifically, in this non-inverting amplifier circuit 1A, the non-inverting input terminal of operational amplifier OP1A is directly connected to signal input ISA, the inverting input terminal is connected to the non-inverting input terminal via resistor R4A and directly connected to the output terminal via resistor R1A, and the output terminal is connected to signal output OSA. In other words, with this configuration, the non-inverting amplifier circuit 1A has the same circuit configuration as the non-inverting amplifier circuit 1X shown in FIG. 9. Therefore, the non-inverting amplifier circuit 1A maintains the excellent high-frequency characteristics of operational amplifier OP1A.

[0034] As described above, with this non-inverting amplifier circuit 1A, by combining two operational amplifiers OP1A and OP2A, even if an offset voltage S or 1 / f noise occurs in the operational amplifier OP1A, the offset voltage S or 1 / f noise can be sufficiently removed and output as the output signal S. Furthermore, with this non-inverting amplifier circuit 1A, it is possible to sufficiently improve the low-frequency characteristics (DC characteristics) while maintaining the good high-frequency characteristics of the operational amplifier OP1A.

[0035] Second Embodiment The non-inverting amplifier circuit 1B shown in FIG. 5 is configured to function as a non-inverting amplifier circuit that non-inverts and amplifies an input signal SINB input via a signal input section ISB with a predetermined gain and outputs the amplified signal as an output signal SOUTB from a signal output section OSB.

[0036] Specifically, the non-inverting amplifier circuit 1B includes an operational amplifier OP1B with good high-frequency characteristics (e.g., good wideband characteristics) that functions as a first operational amplifier B, and an operational amplifier OP2B with good low-frequency characteristics that functions as a second operational amplifier B. Each of the operational amplifiers OP1B and OP2B operates using a power supply voltage that is a positive voltage and a negative voltage that have equal absolute values ​​relative to the ground potential, which serves as an intermediate potential.

[0037] In this case, the operational amplifier OP1B is configured such that its non-inverting input terminal (first B non-inverting input terminal) is connected to the signal input unit ISB via a capacitor C1B (first B capacitor), its inverting input terminal (first B inverting input terminal) is connected to the output terminal (first B output terminal) via a resistor R1B (first B resistor) and to an intermediate potential via a resistor R2B (second B resistor), and its output terminal (first B output terminal) is connected to the signal output unit OSB. The operational amplifier OP2B has a non-inverting input terminal (second B non-inverting input terminal) connected to the signal input section ISB via a resistor R3B (third B resistor), an inverting input terminal (second B inverting input terminal) connected to the inverting input terminal of the operational amplifier OP1B via a resistor R4B (fourth B resistor) and also connected to an output terminal (second B output terminal) via a capacitor C2B (second B capacitor), and an output terminal (second B output terminal) connected to the non-inverting input terminal of the operational amplifier OP1B via a resistor R5B (fifth B resistor).

[0038] Next, the operation of this non-inverting amplifier circuit 1B will be described.

[0039] First, the operation of the non-inverting amplifier circuit 1B when the input signal SINB is a DC signal will be described. When the input signal SINB is a DC signal, the impedance of the capacitors C1B and C2B becomes extremely large, and the resistance values ​​of the resistors R3B, R4b, and R5B are negligible. Therefore, in the non-inverting amplifier circuit 1B, the non-inverting input terminal of the operational amplifier OP1B is equivalently connected to the output terminal of the operational amplifier OP2B, the non-inverting input terminal of the operational amplifier OP2B is open from the signal input section ISB, and is directly connected to the output terminal of the operational amplifier OP2B, the non-inverting input terminal of the operational amplifier OP2B is directly connected to the signal input section ISB, the inverting input terminal of the operational amplifier OP2B is directly connected to the inverting input terminal of the operational amplifier OP1B, and the output terminal of the operational amplifier OP2B is directly connected to the non-inverting input terminal of the operational amplifier OP1B.

[0040] Therefore, when the input signal SINA is a DC signal, the non-inverting amplifier circuit 1B is represented by the circuit configuration shown in Fig. 6. Therefore, in the non-inverting amplifier circuit 1B, the operational amplifier OP1B has an inverting input terminal connected to the output terminal via a resistor R1B and to an intermediate potential via a resistor R2B, and an output terminal connected to a signal output terminal OSB. Also, in the non-inverting amplifier circuit 1B, the operational amplifier OP2B has a non-inverting input terminal connected to a signal input terminal ISB, an inverting input terminal connected to the inverting input terminal of the operational amplifier OP1B, and an output terminal connected to the non-inverting input terminal of the operational amplifier OP1B.

[0041] In this circuit configuration, when the open gain of operational amplifier OP2B is A, the resistance value of resistor R1B is R1B, the resistance value of resistor R2B is R2B, the voltage value of input signal SINB is VINB, the voltage value of output signal SOUTB is VOUTB, the voltage value of offset voltage SOF occurring between the inverting input terminal and non-inverting input terminal of operational amplifier OP1B is VOF, the voltage value of the output terminal of operational amplifier OP2B is V1, and the voltage value of the inverting input terminal of operational amplifier OP1B is V2, the following equation (4) is derived: V1=V2-VOF=(VINB-V2)×A (4)

[0042] Therefore, the following equation (5) is derived from equation (4): (1+A)×V2=VINB×A+VOF (5)

[0043] Here, the voltage value V2 is expressed by the following formula (6): V2=(R2 / (R1+R2))×VOUTB (6)

[0044] Therefore, the voltage value VOUTB of the output signal SOUTB is expressed by the following equation (7) from equations (5) and (6).

[0045] VOUTB=(1+R1 / R2)×(1 / (1+1 / A))×VINB+(1+R1 / R2)×(1 / (1+A))×VOF...Equation (7)

[0046] If the open gain A of the operational amplifier OP2B is sufficiently large, the voltage value VOUTB of the output signal SOUTB is expressed by the following equation (8): VOUTB=((R1+R2) / R2)×VINB (8)

[0047] In other words, with this non-inverting amplifier circuit 1B, even if an offset voltage S or 1 / f noise occurs in the operational amplifier OP1B, it is possible to configure a non-inverting amplifier circuit that can output an output signal S that does not include the offset voltage S or 1 / f noise.

[0048] As shown in Fig. 7, the output signal SOUTY output from the conventional inverting amplifier circuit 1Y has a high level of noise that is considered to be 1 / f noise superimposed in the low frequency range including DC signals. In contrast, as shown in Fig. 8, the output signal SOUTB output from the non-inverting amplifier circuit 1B has a sufficiently reduced level of noise that is considered to be 1 / f noise in the low frequency range including DC signals.

[0049] Next, with reference to FIG. 5, the operation of the non-inverting amplifier circuit 1B when the input signal SINB is a high-frequency signal will be described.

[0050] When the input signal SINA is a high-frequency signal, the impedances of capacitors C1B and C2B are sufficiently small. Therefore, in the non-inverting amplifier circuit 1B, the signal input terminal ISB is shorted to the non-inverting input terminal of the operational amplifier OP1B, causing the operational amplifier OP2B to malfunction. Specifically, in this non-inverting amplifier circuit 1B, the operational amplifier OP1B has its non-inverting input terminal connected directly to the signal input terminal ISA, its inverting input terminal connected to the output terminal via resistor R1A and to an intermediate potential via resistor R2B, and its output terminal connected to the signal output terminal OSA. In other words, with this configuration, the non-inverting amplifier circuit 1B has the same circuit configuration as the non-inverting amplifier circuit 1Y shown in FIG. 10. Therefore, the non-inverting amplifier circuit 1B maintains the excellent high-frequency characteristics of the operational amplifier OP1B.

[0051] As described above, with this non-inverting amplifier circuit 1B, by combining two operational amplifiers OP1B and OP2B, even if an offset voltage S or 1 / f noise occurs in the operational amplifier OP1B, the offset voltage S or 1 / f noise can be sufficiently removed and output as the output signal S. Furthermore, with this non-inverting amplifier circuit 1B, the good high-frequency characteristics of the operational amplifier OP1B can be maintained while the low-frequency characteristics (DC characteristics) can be sufficiently improved.

[0052] The present invention is not limited to the above-described embodiments and can be modified as appropriate. For example, in a non-inverting amplifier circuit 1A, when low-frequency characteristics are required to take priority over high-frequency characteristics for the operational amplifier OP1A, the configuration of Fig. 2 can be adopted. Similarly, in a non-inverting amplifier circuit 1B, when low-frequency characteristics are required to take priority over high-frequency characteristics for the operational amplifier OP1B, the configuration of Fig. 6 can be adopted.

[0053] According to the present invention, even if an offset voltage S or 1 / f noise occurs in an operational amplifier, the offset voltage S or 1 / f noise can be sufficiently removed and output as an output signal, making the present invention widely applicable to such non-inverting amplifier circuits.

[0054] 1A, 1B Non-inverting amplifier circuit C1A, C1B, C2A, C2B Capacitors ISA, ISB Signal input section OSA, OSB Signal output section OP1A, OP1B, OP2A, OP2B Operational amplifier P1 Connection point R1A, R1B, R2A, R2B Resistors SINA, SINB Input signal SOUTA, SOUTB Output signal

Claims

1. A non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a gain of 1 and outputs the amplified signal as an output signal from a signal output section, comprising a first-A operational amplifier and a second-A operational amplifier, wherein the first-A operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to an output terminal via a first-A resistor, and an output terminal connected to the signal output section, and the second-A operational amplifier has a non-inverting input terminal connected to the output terminal of the first-A operational amplifier, an inverting input terminal connected to the signal input section, and an output terminal connected to the inverting input terminal of the first-A operational amplifier via a second-A resistor.

2. A non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a gain of 1 and outputs the amplified signal as an output signal from a signal output section, comprising a first-A operational amplifier and a second-A operational amplifier, wherein the first-A operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to the output terminal via a first-A resistor, and the output terminal connected to the signal output section, the second-A operational amplifier has a non-inverting input terminal connected to the output terminal of the first-A operational amplifier, an inverting input terminal connected to the signal input section via a third-A resistor and to the output terminal via a first-A capacitor, and the output terminal connected to the inverting input terminal of the first-A operational amplifier via a second-A resistor, the second-A resistor being a series circuit of a fourth-A resistor connected to the inverting input terminal of the first-A operational amplifier and a fifth-A resistor connected to the output terminal of the second-A operational amplifier, and the junction of the fourth-A resistor and the fifth-A resistor and the non-inverting input terminal of the first-A operational amplifier are connected by a second-A capacitor.

3. A non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a predetermined gain and outputs the result as an output signal from a signal output section, comprising a first-B operational amplifier and a second-B operational amplifier, wherein the first-B operational amplifier has an inverting input terminal connected to an output terminal via a first-B resistor and to an intermediate potential via a second-B resistor, and the output terminal connected to the signal output section, and the second-B operational amplifier has a non-inverting input terminal connected to the signal input section, an inverting input terminal connected to the inverting input terminal of the first-B operational amplifier, and the output terminal connected to the non-inverting input terminal of the first-B operational amplifier.

4. A non-inverting amplifier circuit that non-inverts and amplifies an input signal input to a signal input section with a predetermined gain and outputs the result as an output signal from a signal output section, comprising a first-B operational amplifier and a second-B operational amplifier, wherein the first-B operational amplifier has a non-inverting input terminal connected to the signal input section via a first-B capacitor, an inverting input terminal connected to the output terminal via a first-B resistor and to an intermediate potential via a second-B resistor, and an output terminal connected to the signal output section, and the second-B operational amplifier has a non-inverting input terminal connected to the signal input section via a third-B resistor, an inverting input terminal connected to the inverting input terminal of the first-B operational amplifier via a fourth-B resistor and to the output terminal via a second-B capacitor, and an output terminal connected to the non-inverting input terminal of the first-B operational amplifier via a fifth-B resistor.

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