A trans-impedance amplifier common mode voltage modulation circuit
By using a transimpedance amplifier common-mode voltage modulation circuit and an operational amplifier detection module to detect the amplitude difference of the photoelectric signal, a pull-back current mirror current source is generated. This solves the problem that the output waveform of the pseudo-differential common-gate TIA cannot adapt to changes in the photoelectric signal, and realizes reliable signal transmission and processing.
Patent Information
- Application Number
- CN202611305371.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-26
- Publication Date
- 2026-11-06
AI Technical Summary
The waveform output by the pseudo-differential common-gate TIA in photoelectric signal processing cannot be directly processed by the subsequent dual-to-single operational amplifier. The fixed common-mode voltage modulation cannot adapt to the amplitude changes of the photoelectric signal, resulting in signal overcorrection or deterioration of the duty cycle, which affects data transmission.
A common-mode voltage modulation circuit for a transimpedance amplifier is designed. The circuit uses a photodiode, a transimpedance amplifier, a detection module, a resistor, and a current source. The detection module, composed of an operational amplifier, detects the signal amplitude difference and generates a pull-back current mirror current source to modulate the waveform common-mode voltage to adapt to changes in the photoelectric signal.
It achieves improved circuit performance at extreme frequencies, ensures reliable transmission and processing of photoelectric signals, avoids signal disturbances, and adaptively adjusts to changes in the amplitude of photoelectric signals.
Smart Images
Figure CN123055004A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit signal link processing technology, and in particular to a common-mode voltage modulation circuit for a transimpedance amplifier. Background Technology
[0002] In the signal chain architecture of photoelectric conversion chips, photodiodes are often used in combination with differential transimpedance amplifiers as the core front-end structure for optical signal reception and weak photoelectric current conversion, and are widely used in analog signal processing scenarios such as optical communication and photoelectric detection.
[0003] Pseudo-differential common-gate (TIA) circuits have advantages such as strong bandwidth adaptability, small parasitic parameters, and simple structure. They are often used as the first-stage amplifier circuit for photoelectric signals. They can convert the weak photocurrent signal output by the photodiode into a voltage signal to provide a voltage signal for the subsequent circuits.
[0004] However, the pseudo-differential common-gate TIA has inherent technical defects in operation; the waveform output by this structure is as follows: Figure 3 The pseudo-differential signal shown cannot be directly processed by the subsequent dual-to-single operational amplifier. Conventional modulation using a fixed common-mode voltage often fails to meet practical applications because the circuit is affected by factors such as fluctuations in light intensity, process deviations, and component temperature drift, causing a significant shift in the common-mode voltage difference between the output signals B1 and A1. If the pullback amplitude is a preset fixed parameter, it cannot adaptively adjust to changes in the amplitude of the photoelectric signal. In extreme cases, when the photoelectric signal amplitude is small, a fixed pullback can easily cause overcorrection, resulting in a fixed output level for the subsequent dual-to-single operational amplifier. When the photoelectric signal amplitude is large, an insufficient fixed pullback amplitude will degrade the duty cycle of the output signal, preventing data transmission at the extreme frequency. Therefore, a design with a fixed preset pullback parameter will lead to chaotic common-mode voltage in the output waveform, making it unsuitable for the subsequent dual-to-single operational amplifier and severely affecting the complete transmission and accurate processing of the photoelectric signal. Summary of the Invention
[0005] The purpose of this invention is to provide a common-mode voltage modulation circuit for a transimpedance amplifier to solve the problems in the prior art.
[0006] To solve the above technical problems, the present invention provides a common-mode voltage modulation circuit for a transimpedance amplifier, comprising: a photodiode, a transimpedance amplifier, a detection module, resistors R1 and R2, a current source I1, and a dual-to-single amplifier; The negative terminal of the photodiode is connected to the power supply, and the positive terminal is connected to the input terminal of the transimpedance amplifier. The output terminals A1 and B1 of the transimpedance amplifier are connected to the first terminals of resistors R1 and R2, respectively. A1 and B1 are also connected to the input terminals of the detection module. The second terminal of resistor R1 is connected to the input terminal A2 of the dual-to-single amplifier, and the second terminal of resistor R2 is connected to the input terminal B2 of the dual-to-single amplifier. Input terminal B2 is connected to the first terminal of current source I1, and the second terminal of current source I1 is grounded. The output terminal of the detection module is connected to current source I1.
[0007] In one embodiment, the detection module includes resistors R3 to R7 and operational amplifiers 1 to 3. The output terminal B1 of the transimpedance amplifier is connected to the first terminal of resistor R3. The second terminal of resistor R3 is connected to both the non-inverting input terminal of operational amplifier 1 and the first terminal of resistor R5. The second terminal of resistor R5 is connected to the reference voltage VBG. The output terminal A1 of the transimpedance amplifier is connected to the first terminal of resistor R4. The second terminal of resistor R4 is connected to both the inverting input terminal of operational amplifier 1 and the first terminal of resistor R6. The second terminal of resistor R6 is connected to the output terminal VO1 of operational amplifier 1. The output terminal VO1 of operational amplifier 1 is connected to the non-inverting input terminal of operational amplifier 2. The output terminal VO2 of operational amplifier 2 is connected to both the inverting input terminal of operational amplifier 2 and the first terminal of resistor R7. The second terminal of resistor R7 is connected to both the inverting input terminal VI3 and the output terminal of operational amplifier 3. The non-inverting input terminal of operational amplifier 3 is connected to the reference voltage VBG.
[0008] This invention provides a common-mode voltage modulation circuit for a transimpedance amplifier, which better enables circuit performance at limiting frequencies and improves the overall reliability of optoelectronic signal operation. The circuit design is simple to implement, and it proposes an effective pull-back solution for situations where the common-mode circuit of the output signal of a pseudo-differential common-gate TIA circuit is not fixed in application. Attached Figure Description
[0009] Figure 1 This is a circuit structure for common-mode voltage modulation of the output of a transimpedance amplifier.
[0010] Figure 2 This is a detection module for a circuit structure applied to common-mode voltage modulation of the output of a transimpedance amplifier.
[0011] Figure 3 This is a schematic diagram of the output waveform of a transimpedance amplifier.
[0012] Figure 4 This is a schematic diagram of the waveform after common-mode modulation of the transimpedance amplifier output. Detailed Implementation
[0013] The common-mode voltage modulation circuit for a transimpedance amplifier proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.
[0014] This invention provides a common-mode voltage modulation circuit for a transimpedance amplifier, the structure of which is as follows: Figure 1 As shown, it includes a photodiode, a transimpedance amplifier, a detection module, resistors R1 and R2, a current source I1, and a dual-to-single amplifier.
[0015] The common-mode voltage modulation circuit of the transimpedance amplifier of the present invention has the following structure: the negative terminal of the photodiode is connected to the power supply, the positive terminal of the photodiode is connected to the input terminal of the transimpedance amplifier, and the output terminals A1 and B1 of the transimpedance amplifier are respectively connected to the first terminals of resistors R1 and R2. Simultaneously, A1 and B1 are connected to the input terminals of the detection module. The second terminal of resistor R1 is connected to the input terminal A2 of the dual-to-single amplifier, and the second terminal of resistor R2 is connected to the input terminal B2 of the dual-to-single amplifier. Simultaneously, input terminal B2 is connected to the first terminal of current source I1, and the second terminal of current source I1 is grounded. The output terminal of the detection module is connected to current source I1.
[0016] The structure of the detection module is as follows Figure 2 As shown, the system includes resistors R3 to R7 and operational amplifiers 1 to 3. Output terminal B1 is connected to the first terminal of resistor R3. The second terminal of resistor R3 is simultaneously connected to the non-inverting input of operational amplifier 1 and the first terminal of resistor R5. The second terminal of resistor R5 is connected to the reference voltage VBG. Output terminal A1 is connected to the first terminal of resistor R4. The second terminal of resistor R4 is simultaneously connected to the inverting input of operational amplifier 1 and the first terminal of resistor R6. The second terminal of resistor R6 is connected to the output terminal VO1 of operational amplifier 1. The output terminal VO1 of operational amplifier 1 is connected to the non-inverting input of operational amplifier 2. The output terminal VO2 of operational amplifier 2 is simultaneously connected to the inverting input of operational amplifier 2 and the first terminal of resistor R7. The second terminal of resistor R7 is simultaneously connected to the inverting input terminal VI3 of operational amplifier 3 and the output terminal of operational amplifier 3. Additionally, the non-inverting input of operational amplifier 3 is connected to the reference voltage VBG.
[0017] The working principle of this invention is as follows: (Let R1=R2, R3=R4, R5=R6=xR3, R7=yR1=yR2) like Figure 1 As shown, the output signals of the transimpedance amplifier's output terminals A1 and B1 are A1 and B1, respectively. When the photodiode is illuminated, it generates signals A1 and B1 as follows: Figure 3As shown, B1 and A1 are square wave waveforms with the same frequency but opposite phase and different high and low levels. The low level of waveform B1 is equal to the high level of waveform A1. The amplitude difference between the high level of waveform B1 and the low level of waveform A1 is VP, which means the difference between the common-mode voltages VCB and VCA of waveforms B1 and A1 is 1 / 2VP.
[0018] The input signals to the dual-to-single amplifier are A2 and B2, respectively. The detection module detects the amplitude difference between the waveforms A1 and B1, generating a pull-back current mirror current source I1. The modulated waveforms A2 and B2 are as follows: Figure 4 As shown, waveform A2 is identical to waveform A1. Waveform B2 is based on waveform B1, but the common-mode point is pulled down from VCB to VCA, while the frequency and amplitude remain unchanged. At this point, waveforms B2 and A2 have the same common-mode voltage, forming a standard differential signal.
[0019] Detection module such as Figure 2 As shown, signals A1 and B1 pass through operational amplifier 1 and the proportional amplifier composed of resistors R3~R6, and VO1 can be calculated as x*(VB1-VA1)+VBG. Since operational amplifier 2 is an ideal amplifier, VO2=VO1, and operational amplifier 2's output current-pull capability is stronger than its current-sinking capability, ensuring that VO2 detects the highest amplitude of signals A1 and B1 and outputs it stably. Because of operational amplifier 3, VI3=VBG. Therefore, the current IR7 on R7 = (VO2-VI3) / R7 = (VO1-VBG) / R7 = x(VB1-VA1) / yR2.
[0020] 4. The output current IR7 of the detection module is mirrored 1:1 as the current source I1. The pullback amplitude is designed to be 1 / 2 (VB1-VA1), resulting in I1R2 = x(VB1-VA1)*R2 / yR2 = x / y(VB1-VA1). The ratio of x to y is set to 1:2, which meets the design requirements. The values of R1 to R7 will be selected based on the actual circuit characteristics.
[0021] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A transimpedance amplifier common mode voltage modulation circuit, comprising: include: Photodiode, transimpedance amplifier, detection module, resistors R1 and R2, current source I1, dual-to-single amplifier; The negative terminal of the photodiode is connected to the power supply, and the positive terminal is connected to the input terminal of the transimpedance amplifier. The output terminals A1 and B1 of the transimpedance amplifier are connected to the first terminals of resistors R1 and R2, respectively. A1 and B1 are also connected to the input terminals of the detection module. The second terminal of resistor R1 is connected to the input terminal A2 of the dual-to-single amplifier, and the second terminal of resistor R2 is connected to the input terminal B2 of the dual-to-single amplifier. Input terminal B2 is connected to the first terminal of current source I1, and the second terminal of current source I1 is grounded. The output terminal of the detection module is connected to current source I1.
2. The transimpedance amplifier common mode voltage modulation circuit of claim 1, wherein, The detection module includes resistors R3 to R7 and operational amplifiers 1 to 3. The output terminal B1 of the transimpedance amplifier is connected to the first terminal of resistor R3. The second terminal of resistor R3 is connected to both the non-inverting input terminal of operational amplifier 1 and the first terminal of resistor R5. The second terminal of resistor R5 is connected to the reference voltage VBG. The output terminal A1 of the transimpedance amplifier is connected to the first terminal of resistor R4. The second terminal of resistor R4 is connected to both the inverting input terminal of operational amplifier 1 and the first terminal of resistor R6. The second terminal of resistor R6 is connected to the output terminal VO1 of operational amplifier 1. The output terminal VO1 of operational amplifier 1 is connected to the non-inverting input terminal of operational amplifier 2. The output terminal VO2 of operational amplifier 2 is connected to both the inverting input terminal of operational amplifier 2 and the first terminal of resistor R7. The second terminal of resistor R7 is connected to both the inverting input terminal VI3 and the output terminal of operational amplifier 3. The non-inverting input terminal of operational amplifier 3 is connected to the reference voltage VBG.