Amplifier circuit

Abstract

An amplifier circuit includes a programmable gain amplifier, a first resistor, a second resistor, and at least one third resistor. The programmable gain amplifier is provided with a first positive input end, a first negative input end, a second positive input end, a second negative input end, a positive output end and a negative output end. The first resistor is connected between the first negative input terminal and the positive output terminal. One end of the second resistor is connected to the first negative input end and the first resistor, and the other end is connected to the second positive input end. The at least one third resistor is connected between the second positive input end and the negative output end. The sum of the resistance value of the first resistor and the resistance value of the second resistor is the same as the resistance value of the at least one third resistor.

Description

Technical Field

[0001] The present invention relates to an amplifier circuit, and particularly to an amplifier circuit that can improve the distortion problem of the output signal without an additional single-ended to differential-ended circuit. Background Art

[0002] In the architecture of a differential difference amplifier (DDA), as the amplitude of the input signal increases, it is easily affected by resistor feedback, resulting in a sharp deterioration of the linearity of the output signal line and causing distortion in subsequent signal processing. Therefore, if the differential amplifier architecture is to operate under large signal amplitudes, it is only suitable for differential input and not suitable for circuit applications with single-ended input converted to differential output. Summary of the Invention

[0003] In view of the above, an object of the present invention is to provide an amplifier circuit that can improve the problem of output signal distortion without an additional single-ended to differential-ended circuit.

[0004] An amplifier circuit according to an embodiment of the present invention includes a programmable gain amplifier, a first resistor, a second resistor, and at least one third resistor. The programmable gain amplifier has a first positive input terminal, a first negative input terminal, a second positive input terminal, a second negative input terminal, a positive output terminal, and a negative output terminal. The first resistor is connected between the first negative input terminal and the positive output terminal. One end of the second resistor is connected to the first negative input terminal and the first resistor, and the other end is connected to the second positive input terminal. The at least one third resistor is connected between the second positive input terminal and the negative output terminal. The sum of the resistance values of the first resistor and the second resistor is the same as the resistance value of the at least one third resistor.

[0005] With the above structure, in the amplifier circuit disclosed by the present invention, by specially designing the impedance values between specific terminals of the programmable gain amplifier, a non-inverting amplifier structure can be formed between the first positive input terminal and the first negative input terminal of the programmable gain amplifier, and an inverting amplifier structure can be formed between the second positive input terminal and the second negative input terminal. Regarding the selection of the resistance values of the resistors, the sum of the resistance values of the first resistor connected between the first negative input terminal and the positive output terminal and the second resistor connected to the first negative input terminal and the first resistor is used as a reference value, and the resistance value of at least one third resistor connected between the second positive input terminal and the negative output terminal is made the same as the reference value. In this way, the effect of overcoming signal distortion can be achieved when the amplitude of the single-ended input signal is large, and there is no need to set an additional single-ended to differential-ended circuit.

[0006] The above description of the content of the present invention and the following description of the embodiments are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation for the protection scope of the present invention. Description of the Drawings

[0007] Figure 1 It is a circuit diagram of an amplifier circuit shown according to an embodiment of the present invention.

[0008] Figure 2 It is a circuit diagram of an amplifier circuit shown according to another embodiment of the present invention.

[0009] Figure 3 It is a signal schematic diagram of an amplifier circuit shown according to an embodiment of the present invention.

[0010]

Description of the Reference Numerals

[0011] 1, 1’: Amplifier circuit

[0012] 11: Programmable gain amplifier

[0013] 111: First positive input terminal

[0014] 112: First negative input terminal

[0015] 113: Second positive input terminal

[0016] 114: Second negative input terminal

[0017] 115: Positive output terminal

[0018] 116: Negative output terminal

[0019] 12: First resistor

[0020] 13: Second resistor

[0021] 14, 15, 18: Third resistor

[0022] 16: First capacitor

[0023] 17: Second capacitor

[0024] VIP: AC input signal

[0025] VIP-: AC feedback signal

[0026] VOP: Positive output signal

[0027] VON: Negative output signal

[0028] VCM: Common mode signal

[0029] VIN+: Common mode feedback signal Detailed Embodiments

[0030] The following describes in detail the detailed features and advantages of the present invention in the embodiments. The content is sufficient for those of ordinary skill in the art to understand the technical content of the present invention and implement it accordingly. According to the content, protection scope and drawings disclosed in this specification, those of ordinary skill in the art can easily understand the related purposes and advantages of the present invention. The following embodiments further illustrate the viewpoints of the present invention in detail, but do not limit the scope of the present invention in any way.

[0031] Please refer to Figure 1 , Figure 1 an amplifier circuit shown according to an embodiment of the present invention. As Figure 1 shown, the amplifier circuit 1 includes a programmable gain amplifier 11, a first resistor 12, a second resistor 13, two third resistors 14, 15, a first capacitor 16, and a second capacitor 17. The programmable gain amplifier 11 has a first positive input terminal 111, a first negative input terminal 112, a second positive input terminal 113, a second negative input terminal 114, a positive output terminal 115, and a negative output terminal 116. The first resistor 12 is connected between the first negative input terminal 112 and the positive output terminal 115. One end of the second resistor 13 is connected to the first negative input terminal 112 and the first resistor 12, and the other end is connected to the second positive input terminal 113. The third resistor 14 is connected between the second positive input terminal 113 and the third resistor 15. The third resistor 15 is connected between the third resistor 14 and the negative output terminal 116. The first resistor 12 and the third resistor 15 have the same resistance value. The second resistor 13 and the third resistor 14 have the same resistance value. It should be noted that the first capacitor 16 and the second capacitor 17 of the amplifier circuit 1 are selectively provided.

[0032] In this example, the programmable gain amplifier (PGA) 11 is an amplifier that allows the user to adjust the gain and has a high input impedance, and has four input terminals and two output terminals (differential output). Specifically, the programmable gain amplifier 11 may internally include two operational amplifiers. The positive input terminal of the first operational amplifier may correspond to the first positive input terminal 111, the negative input terminal of the first operational amplifier may correspond to the first negative input terminal 112, the positive input terminal of the second operational amplifier may correspond to the second positive input terminal 113, the negative input terminal of the second operational amplifier may correspond to the second negative input terminal 114, the output terminal of the first operational amplifier may correspond to the positive output terminal 115, and the output terminal of the second operational amplifier may correspond to the negative output terminal 116. However, the above is only for illustrative purposes, and the present invention is not limited thereto.

[0033] By connecting the respective terminals of the programmable gain amplifier 11, amplifier circuits with different functions can be generated. For example, Figure 1 as shown, in this example, the first negative input terminal 112 of the amplifier circuit 1 is connected to the positive output terminal 115 and the first positive input terminal 111 receives an input signal. Therefore, the above first operational amplifier can be called a non-inverting amplifier. The second positive input terminal 113 of the amplifier circuit 1 is connected to the negative output terminal 116 and the second negative input terminal 114 receives another input signal. Therefore, the above second operational amplifier can be called an inverting amplifier.

[0034] In this example, the first resistor 12 is connected between the first negative input terminal 112 and the positive output terminal 115. One end of the second resistor 13 is connected to the first negative input terminal 112 and the other end is connected to the second positive input terminal 113. The third resistors 14 and 15 are connected in series with each other and are connected between the second positive input terminal 113 and the negative output terminal 116. The first resistor 12 and the third resistor 15 have the same resistance value Rf. In addition, the second resistor 13 and the third resistor 14 in this example may have the same resistance value Rs. Through the above configuration, the gain value of the amplifier circuit 1 in this example can be expressed by the following relational expression, where G is the gain value.

[0035] Relational expression: G = (Rs + Rf) / Rs

[0036] Furthermore, the selection of the resistance value is also related to the noise and power consumption that the amplifier circuit 1 is intended to present. For example, the smaller the resistance value, the smaller the circuit noise (thermal noise is 4kTR, where k is the Boltzmann constant, T is the temperature, and R is the resistance), and the greater the power consumption (P = V 2 / R, where P is the power consumption, V is the voltage, and R is the resistance); the larger the resistance value, the greater the circuit noise and the smaller the power consumption. In addition to the resistors, the amplifier circuit 1 in this example may further include a first capacitor 16 and a second capacitor 17. One end of the first capacitor 16 is connected to the positive output terminal 115 and the other end is connected to the first negative input terminal 112. One end of the second capacitor 17 is connected to the negative output terminal 116 and the other end is connected between the third resistor 14 and the third resistor 15, where the first capacitor 16 and the second capacitor 17 have the same capacitance value. Through the first capacitor 16 and the second capacitor 17, high-frequency noise can be filtered, further improving the quality of signal processing. It should be noted that the first capacitor 16 and the second capacitor 17 can also be selectively provided. It should be noted that the capacitors in this example, as low-pass filters, can filter high-frequency noise outside the signal frequency band input at the first positive input terminal 111 by selecting a specific capacitance value. And if the signal input at the first positive input terminal 111 is an extremely high-frequency signal, it may not be necessary to provide a capacitor.

[0037] Please refer to Figure 2 , Figure 2 which is the circuit diagram of the amplifier circuit shown according to another embodiment of the present invention. As Figure 2 shown, in this example, the programmable gain amplifier 11 of the amplifier circuit 1' (including the first positive input terminal 111, the first negative input terminal 112, the second positive input terminal 113, the second negative input terminal 114, the positive output terminal 115, and the negative output terminal 116), the first resistor 12, the second resistor 13, the first capacitor 16, and the second capacitor 17, and the connection relationships between the components can be the same as those in Figure 1 the embodiment. In contrast, the second capacitor 17 in this example can be directly connected between the second positive input terminal 113 and the negative output terminal 116, the third resistor 18 is directly connected between the second positive input terminal 113 and the negative output terminal 116, and can correspond to Figure 1 the third resistors 14 and 15 in the embodiment. In other words, the second capacitor 17 and the third resistor 18 in this example are connected in parallel with each other and connected between the second positive input terminal 113 and the negative output terminal 116. In this example, the resistance value of the third resistor 18 is the sum of the resistance values of the third resistors 14 and 15 in the previous example, that is, equivalent to the sum of the resistance values of the first resistor 12 and the second resistor 13. Additionally, in some embodiments, the third resistor 18 can be formed by connecting multiple resistors in series.

[0038] In application, the first positive input terminal 111 of the above amplifier circuits 1 and 1' can be used to receive an AC input signal (VIP), and the second negative input terminal 114 can be used to receive a DC signal (VCM). Please combine Figure 1 or Figure 2 refer to Figure 3 , Figure 3 which is the signal schematic diagram of the amplifier circuit shown according to an embodiment of the present invention. Figure 3 Schematically shows the waveform of the AC input signal VIP received by the first positive input terminal 111, the waveform of the AC feedback signal VIP- transmitted by the first negative input terminal 112, the waveform of the common-mode signal VCM received by the second negative input terminal 114, the waveform of the common-mode feedback signal VIN+ transmitted by the second positive input terminal 113, the waveform of the positive output signal VOP output by the positive output terminal 115, and the waveform of the negative output signal VON output by the negative output terminal 116. As Figure 2 shown, for example, the amplitude of the AC input signal VIP input from the first positive input terminal 111 is between about 1.1 and 1.2 volts (V), and the period is about 1 millisecond (ms). In contrast, the common-mode signal VCM input from the second negative input terminal 114 is a DC signal, and its level is about 0.8 volts (V). Therefore, the amplifier circuit 1 in this example adopts the single-ended input signal mode.

[0039] When the first positive input terminal 111 and the second negative input terminal 114 receive the AC input signal VIP and the common-mode signal VCM respectively, the programmable gain amplifier 11 can generate an AC feedback signal VIP- at the first negative input terminal 112 and a common-mode feedback signal VIN+ at the second positive input terminal 113 through the above components and circuit connection relationships. Specifically, the AC feedback signal VIP- has the same phase and similar amplitude as the AC input signal VIP, and the common-mode feedback signal VIN+ has the same voltage level as the common-mode signal VCM.

[0040] Furthermore, the programmable gain amplifier 11 can generate a positive output signal VOP at the positive output terminal 115 and a negative output signal VON at the negative output terminal 116 through the above components and circuit connection relationships. The positive output signal VOP has the same phase as the AC input signal VIP. The positive output signal VOP and the negative output signal VON have opposite polarities (the phase difference is 180 degrees) and the same amplitude. Specifically, the amplitudes of the positive output signal VOP and the negative output signal VON are determined by the above gain value. In this example, the amplitudes of the positive output signal VOP and the negative output signal VON are approximately 1.3 to 1.4 volts (V).

[0041] Through the amplifier circuits 1 and 1' described above, it is possible to apply to single-ended input applications that require analog-to-digital conversion, such as microphones, touch panels, etc.

[0042] With the above structure, the amplifier circuit disclosed in the present invention can form a non-inverting amplifier structure between the first positive input terminal and the first negative input terminal of the programmable gain amplifier and an inverting amplifier structure between the second positive input terminal and the second negative input terminal by specifically designing the impedance value between specific terminals of the programmable gain amplifier. Regarding the selection of the resistance value of the resistor, the sum of the resistance values of the first resistor connected between the first negative input terminal and the positive output terminal and the second resistor connected between the first negative input terminal and the first resistor is used as a reference value, and the resistance value of at least one third resistor connected between the second positive input terminal and the negative output terminal is made the same as the reference value. In this way, the effect of overcoming signal distortion can be achieved when the amplitude of the single-ended input signal is large. In addition, by respectively setting filter capacitors in the above non-inverting amplifier and inverting amplifier, high-frequency noise can be filtered, further improving the quality of signal processing.

Claims

1. An amplifier circuit, characterized in that, Comprising: A programmable gain amplifier having a first positive input terminal, a first negative input terminal, a second positive input terminal, a second negative input terminal, a positive output terminal, and a negative output terminal; A first resistor connected between the first negative input terminal and the positive output terminal; A second resistor having one end connected to the first negative input terminal and the first resistor and the other end connected to the second positive input terminal; At least one third resistor connected between the second positive input terminal and the negative output terminal, wherein the sum of the resistance values of the first resistor and the second resistor is the same as the resistance value of the at least one third resistor.

2. The amplifier circuit according to claim 1, wherein, The first positive input terminal is used to receive an AC signal, and the second negative input terminal is used to receive a DC signal.

3. The amplifier circuit according to claim 1, characterized in that, The number of the at least one third resistor is two. One end of the first of the at least one third resistors is connected to the second positive input terminal, and one end of the second of the at least one third resistors is connected to the negative output terminal.

4. The amplifier circuit according to claim 3, wherein The resistance value of the first of the at least one third resistors is the same as the resistance value of the second resistor, and the resistance value of the second of the at least one third resistors is the same as the resistance value of the first resistor.

5. The amplifier circuit according to claim 1, wherein Further comprising a first capacitor having one end connected to the positive output terminal and the other end connected to the first negative input terminal.

6. The amplifier circuit according to claim 3, wherein Further comprising a second capacitor having one end connected to the negative output terminal and the other end connected between the first and the second of the at least one third resistors.

7. The amplifier circuit according to claim 1, characterized in that, Further comprising a second capacitor having one end connected to the negative output terminal and the other end connected to the second positive input terminal.

8. The amplifier circuit according to claim 3, characterized in that, Further comprising a first capacitor and a second capacitor. The first capacitor has one end connected to the positive output terminal and the other end connected to the first negative input terminal. The second capacitor has one end connected to the negative output terminal and the other end connected between the first and the second of the at least one third resistors.

9. The amplifier circuit according to claim 1, wherein Further comprising a first capacitor and a second capacitor. The first capacitor has one end connected to the positive output terminal and the other end connected to the first negative input terminal. The second capacitor has one end connected to the negative output terminal and the other end connected to the second positive input terminal.

10. The amplifier circuit according to claim 8 or 9, characterized in that, The first capacitor and the second capacitor have the same capacitance value.

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