A kind of regulating circuit of transimpedance amplifier output signal

Abstract

This invention provides a circuit for adjusting the output signal of a transimpedance amplifier, comprising a transimpedance amplifier, a light-free unit, a signal processing unit, and a control unit. The transimpedance amplifier processes a current signal to obtain a voltage signal. The light-free unit generates a static voltage for photoelectric conversion when there is no light source input. The signal processing unit detects the static voltage and the average voltage of the voltage signal, and obtains an amplified voltage based on the voltage signal and the average voltage of the voltage signal. The input terminal of the control unit is connected to the output terminal of the signal processing unit, and the output terminal of the control unit is connected to the input terminals of the light-free unit and the transimpedance amplifier. The control unit generates a control signal based on the amplified voltage. The control signal adjusts the static voltage of the light-free unit and the DC signal of the transimpedance amplifier to change the output voltage signal of the transimpedance amplifier. This invention can reduce the jitter of the output voltage signal of the transimpedance amplifier and improve the accuracy of the output voltage signal.

Description

Technical Field

[0001] This invention relates to the field of signal processing technology, and in particular to a circuit for adjusting the output signal of a transimpedance amplifier. Background Technology

[0002] In various applications requiring photoelectric conversion, transimpedance amplifiers (TIAs) are a common method for converting current signals detected by diodes (photodetector diodes PD or avalanche photodiodes APD) into voltage signals.

[0003] A typical single-ended transimpedance amplifier (TIA) circuit structure is as follows: Figure 1 APD / PD converts optical signals into... Figure 2 The current signal shown is converted into a voltage signal Von by the transimpedance amplifier. Due to the unidirectional current flow characteristic of the diode, the current waveform output by the PD or APD is as follows: Figure 2 When there is a signal, current flows; when there is no signal, the current is zero, i.e., the current is 0 when there is no light input. When there is light input, pulse currents I0 and I1 are generated. Current I1 corresponds to a signal level of 1, and current I0 corresponds to a signal level of 0. The ratio of currents I1 and I0 corresponds to the extinction ratio ER = 10log(I1 / I0). Figure 3 The output voltage waveform is shown in Figure 1. This figure shows the voltage waveform of the output voltage Von of a transimpedance amplifier (TIA) without DC cancellation.

[0004] To eliminate direct current, the following is proposed: Figure 4 The diagram shows an improved transimpedance amplifier, specifically a DC-canceling transimpedance amplifier, which adds a DC cancellation circuit section. Under sufficiently high gain, Ios is approximately equal to the average current of PD / APD. The waveforms at various points are shown below. Figure 5 (1), for Figure 5 The current I generated by the diode in (1) passes through Figure 5 (2) The Ios feedback to the input of the transimpedance amplifier can eliminate DC, so that the final current I input to the transimpedance amplifier is as follows: Figure 5 (3) As shown; when the transimpedance amplifier is in a static state without light input, the output voltage V is V0. When there is light input, the output voltage fluctuates around V0 as follows: Figure 6 As shown, when the value of V0 is too low or too high, if the signal swing is large, the active devices in the circuit have saturation, cutoff and linear operating regions. The signal will enter the saturation region or cutoff region, which will cause signal distortion. Finally, it will be converted into duty cycle distortion, which will become jitter and affect the accuracy of signal output. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an adjustment circuit for the output signal of a transimpedance amplifier, which solves the problem of jitter in the output waveform of a transimpedance amplifier in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a circuit for adjusting the output signal of a transimpedance amplifier, comprising a transimpedance amplifier, a light-free unit, a signal processing unit, and a control unit;

[0007] The input terminal of the transimpedance amplifier is connected to the current signal generated by photoelectric conversion, and the current signal is processed to obtain a voltage signal.

[0008] The light-free unit is used to generate the static voltage of photoelectric conversion when there is no light source input;

[0009] The input terminal of the signal processing unit is connected to the output terminal of the light-free unit and the output terminal of the transimpedance amplifier. The signal processing unit detects the static voltage and the average voltage of the voltage signal, and obtains the amplified voltage based on the voltage signal and the average voltage of the voltage signal.

[0010] The input terminal of the control unit is connected to the output terminal of the signal processing unit, the first output terminal of the control unit is connected to the light-free unit, and the second output terminal of the control unit is connected to the input terminal of the transimpedance amplifier; the control unit generates a control signal based on the amplified voltage.

[0011] The control signal adjusts the static voltage of the light-free unit and the DC signal of the transimpedance amplifier to change the voltage signal output by the transimpedance amplifier.

[0012] Preferably, the control signal includes a first regulating current and a second regulating current, wherein the first regulating current is output to the light-free unit through the first output terminal of the control unit to regulate the static voltage;

[0013] The second regulating current is output to the transimpedance amplifier through the second output terminal of the control unit to eliminate DC in the current signal.

[0014] Preferably, the control unit includes a first adjustment module and a second adjustment module;

[0015] The first adjustment module includes a first current mirror, which is connected to the input terminal of the transimpedance amplifier and the output terminal of the signal processing unit. The first current mirror converts the amplified voltage into a first adjustment current.

[0016] The second adjustment module includes a second current mirror and a current processing submodule; the second current mirror is connected to the output terminals of the light-free unit and the signal processing unit, and the second current mirror converts the amplified voltage to obtain an intermediate current.

[0017] Preferably, the current processing submodule includes a first current mirror pair and a second current mirror pair; the first current mirror pair and the second current mirror pair sequentially perform polarity conversion on the intermediate current and output a second regulating current.

[0018] Preferably, the first current mirror and the second current mirror have the same structure, and the component size ratio between them is M:1; the first current mirror pair and the second current mirror pair have the same structure, and the component size ratio between them is N:1, where M and N are positive integers.

[0019] Preferably, the adjustment circuit further includes a differential amplifier;

[0020] The inverting input of the differential amplifier is connected to the output of the transimpedance amplifier to receive the voltage signal; the non-inverting input of the differential amplifier is connected to a reference voltage; and the control terminal of the differential amplifier receives a gain control signal.

[0021] The differential amplifier processes the voltage signal and the reference signal based on the gain control signal to obtain the output voltage.

[0022] Preferably, the control unit further includes a third current mirror, which is connected to the output terminal of the signal processing unit and the control terminal of the differential amplifier. The third current mirror converts the amplified voltage into a third regulating current, wherein the third regulating current serves as the gain control signal of the differential amplifier.

[0023] Preferably, the first current mirror, the second current mirror, and the third current mirror are all voltage-controlled current sources.

[0024] As described above, the complete invention title has the following beneficial effects:

[0025] The present invention relates to a transimpedance amplifier output signal adjustment circuit that, while eliminating DC current, adjusts the static voltage of the transimpedance amplifier to keep the current operating in the linear region, thereby reducing saturation and cutoff distortion, and thus reducing the jitter of the output voltage signal and improving its accuracy. Simultaneously, a differential amplifier is added; this differential amplifier with gain control allows for gain control of the output voltage signal of the transimpedance amplifier, thereby achieving the technical objective of improving the duty cycle. Attached Figure Description

[0026] Figure 1 The diagram shown is a typical circuit diagram of a single-ended transimpedance amplifier in the prior art.

[0027] Figure 2 The diagram shows the current waveform of the diode output in a typical circuit of a single-ended transimpedance amplifier in the prior art.

[0028] Figure 3 The diagram shows a typical circuit output voltage waveform of a single-ended transimpedance amplifier in the prior art.

[0029] Figure 4 The diagram shows a circuit schematic of a transimpedance amplifier that eliminates DC current in the prior art.

[0030] Figure 5 The diagram shows the waveforms of various currents in a prior art transimpedance amplifier circuit that eliminates DC current.

[0031] Figure 6 The diagram shows a waveform of the output voltage signal of a transimpedance amplifier circuit that eliminates DC current in the prior art.

[0032] Figure 7 The diagram shown is a schematic of the adjustment circuit for the output signal of the transimpedance amplifier in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached diagram: 1. Transimpedance amplifier; 2. Light source-less unit; 3. Signal processing unit; 4. Control unit. Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] Please see Figure 7 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0036] This invention proposes a circuit for adjusting the output signal of a transimpedance amplifier, comprising a transimpedance amplifier 1, a light-free unit 2, a signal processing unit 3, and a control unit 4;

[0037] The input terminal of the transimpedance amplifier is connected to the current signal generated by photoelectric conversion, and the current signal is processed to obtain a voltage signal.

[0038] The light-free unit is used to generate the static voltage of photoelectric conversion when there is no light source input;

[0039] The input terminal of the signal processing unit is connected to the output terminal of the light-free unit and the output terminal of the transimpedance amplifier. The signal processing unit detects the static voltage and the average voltage of the voltage signal, and obtains the amplified voltage based on the voltage signal and the average voltage of the voltage signal.

[0040] The input terminal of the control unit is connected to the output terminal of the signal processing unit, the first output terminal of the control unit is connected to the light-free unit, and the second output terminal of the control unit is connected to the input terminal of the transimpedance amplifier; the control unit generates a control signal based on the amplified voltage.

[0041] The control signal adjusts the static voltage of the light-free unit and the DC signal of the transimpedance amplifier to change the voltage signal output by the transimpedance amplifier.

[0042] The adjustment circuit for the output signal of the transimpedance amplifier of the present invention adjusts the static voltage of the transimpedance amplifier to make the current work in the linear region on the basis of eliminating DC, thereby reducing the occurrence of saturation and cutoff distortion, thereby reducing the jitter of the output voltage signal of the transimpedance amplifier and improving the accuracy of the output voltage signal.

[0043] The control signals of the present invention include a first regulating current and a second regulating current, wherein the first regulating current is output to the light-free unit through the first output terminal of the control unit to regulate the static voltage;

[0044] The second regulating current is output to the transimpedance amplifier through the second output terminal of the control unit to eliminate DC in the current signal.

[0045] Specifically, the control unit of the present invention eliminates DC in the current signal by means of a first regulating current and adjusts the static voltage of the transimpedance amplifier by means of a second regulating current, so that the current operates in the linear region to reduce the occurrence of saturation and cutoff distortion, thereby reducing the jitter of the voltage signal output by the transimpedance amplifier.

[0046] The control unit of the present invention includes a first adjustment module and a second adjustment module;

[0047] The first adjustment module includes a first current mirror M1, which is connected to the input terminal of the transimpedance amplifier and the output terminal of the signal processing unit. The first current mirror M1 converts the amplified voltage into a first adjustment current I1.

[0048] The second adjustment module includes a second current mirror M2 and a current processing submodule; the second current mirror M2 is connected to the output terminals of the light-free unit and the signal processing unit, and the second current mirror M2 converts the amplified voltage to obtain an intermediate current; wherein, the first current mirror M1 and the second current mirror M2 have the same structure.

[0049] The current processing submodule of the present invention includes a first current mirror pair and a second current mirror pair; the first current mirror pair and the second current mirror pair sequentially perform polarity conversion on the intermediate current and output a second regulating current I2.

[0050] The first current mirror M1 and the second current mirror M2 of the present invention have the same structure and their component size ratio is M:1. The first current mirror pair MN1 and the second current mirror pair MN2 have the same structure and their component size ratio is N:1.

[0051] In the control unit of this invention, the first current mirror M1 and the second current mirror M2 are voltage-controlled current sources, and the amplified voltage is generated by the controlled signal processing unit.

[0052] When the gain of the integrating amplifier IA in the first current mirror M1 and the signal processing unit is sufficiently large, the first regulating current I1 is approximately equal to the average current of the photoelectric conversion unit.

[0053] In this invention, the first regulating current I1 and the second regulating current generated by the controlled amplification voltage are respectively input to the input terminal of the transimpedance amplifier and the light-free unit. The second regulating current I2 is input to the light-free unit to enable the light-free unit to be in a state where the light-free unit is not in use. Specifically, the magnitude of the first regulating current I1 is changed by adjusting the magnitudes of the proportional values ​​M and N, thereby changing the DC current at the input terminal of the transimpedance amplifier 1, thus changing the DC operating point V0 of the transimpedance amplifier, so that the AC swing of the input current operates in the linear region, reducing saturation and cutoff distortion, and achieving reduced jitter.

[0054] Specifically, the second regulating current I2 = I1 / MN. As the signal of the intermediate current output by the second current mirror M2 changes, the static voltage V` also changes. The first regulating current I1 changes, which ultimately causes the voltage signal V output by the transimpedance amplifier to change as well. When the static voltage V` becomes higher, the voltage signal V output by the transimpedance amplifier becomes higher.

[0055] The adjustment circuit of the present invention also includes a differential amplifier;

[0056] The inverting input of the differential amplifier is connected to the output of the transimpedance amplifier to receive the voltage signal; the non-inverting input of the differential amplifier is connected to a reference voltage; and the control terminal of the differential amplifier receives a gain control signal.

[0057] The differential amplifier processes the voltage signal and the reference signal based on the gain control signal to obtain the output voltage.

[0058] The adjustment circuit of this invention adds a differential amplifier, which can control the gain of the voltage signal output by the transimpedance amplifier through the differential amplifier with gain control, thereby achieving the technical objective of improving the duty cycle.

[0059] The control unit of the present invention further includes a third current mirror M3, which is connected to the output terminal of the signal processing unit and the control terminal of the differential amplifier. The third current mirror M3 converts the amplified voltage into a third adjustment current I3, wherein the third adjustment current I3 serves as the gain control signal of the differential amplifier.

[0060] The control unit of the present invention also uses the third regulating current I3 generated by the amplified voltage as the gain control signal of the differential amplifier, so that the differential amplifier DA operates in the linear region to reduce distortion, thereby further improving the duty cycle and waveform of the output voltage.

[0061] The third current mirror M3 of this invention is also a voltage-controlled current source, which is an amplified voltage generated by the controlled signal processing unit.

[0062] The regulating circuit of the present invention includes a photoelectric conversion unit, which receives an optical signal and converts the optical signal to generate a current signal.

[0063] In this embodiment of the invention, the photoelectric conversion unit includes a photodetector diode or an avalanche photodiode.

[0064] The structure of the light-free unit and the transimpedance amplifier of this invention is the same.

[0065] The transimpedance amplifier includes a first operational amplifier A1 and a first feedback resistor R. F The first operational amplifier A1 and the first feedback resistor R F In parallel configuration, the input terminal of the first operational amplifier A1 is the input terminal of the transimpedance amplifier, and the output terminal of the first operational amplifier A1 is the output terminal of the transimpedance amplifier.

[0066] The transimpedance amplifier 1 of the present invention converts the current signal I into a voltage signal V, where V = I × R F .

[0067] The light-free unit includes a second operational amplifier A2 and a second feedback resistor R' F The second operational amplifier A2 and the second feedback resistor R` F The second operational amplifier A2 is connected in parallel, and its output is the output of the light-free unit. The temperature and process deviation of the light-free unit are the same as those of the transimpedance amplifier, and the output is a static voltage without an input light source.

[0068] Since the light-free unit of the present invention does not have a current signal generated by the photoelectric conversion unit, a static voltage is generated in the absence of an input current signal. That is, the static voltage is the DC voltage of the transimpedance amplifier 1 when there is no input current signal.

[0069] The signal processing unit of this invention includes a filtering module and an integrating amplifier IA;

[0070] The input terminal of the filter module is connected to the output terminal of the transimpedance amplifier, and the output terminal of the filter module is connected to the inverting input terminal of the integrating amplifier IA. The filter module is used to obtain the average voltage of the voltage signal.

[0071] The non-inverting input terminal of the integrating amplifier IA is connected to the output terminal of the light-free unit to obtain the static voltage;

[0072] The integrating amplifier IA processes the average voltage and static voltage of the voltage signal to obtain the amplified voltage.

[0073] The signal judgment module of the present invention detects the average voltage and static voltage of the transimpedance amplifier 1, and compares and amplifies the voltage difference between the two to obtain the amplified voltage.

[0074] In this embodiment of the invention, the filtering module in the signal processing unit includes a filtering resistor RC and a first capacitor C1. One end of the filtering resistor RC is connected to the input terminal of the transimpedance amplifier, and the other end is connected to the inverting input terminal of the integrating amplifier IA. One end of the first capacitor C1 is connected to the inverting input terminal of the integrating amplifier IA, and the other end is grounded.

[0075] In this embodiment of the invention, the signal processing unit further includes a second capacitor C2, one end of which is connected to the non-inverting input terminal of the integrating amplifier IA, and the other end is grounded.

[0076] In summary, the adjustment circuit for the output signal of the transimpedance amplifier in this invention, by eliminating DC current, adjusts the static voltage of the transimpedance amplifier to keep the current operating in the linear region, thereby reducing saturation and cutoff distortion, and thus reducing the jitter of the output voltage signal and improving its accuracy. Simultaneously, the addition of a differential amplifier, with gain control, allows for gain control of the output voltage signal, thereby improving the duty cycle. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0077] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A transimpedance amplifier output signal conditioning circuit, comprising: It includes a transimpedance amplifier, a light-free unit, a signal processing unit, and a control unit; The input terminal of the transimpedance amplifier is connected to the current signal generated by photoelectric conversion, and the current signal is processed to obtain a voltage signal. The light-free unit is used to generate the static voltage of photoelectric conversion when there is no light source input; The input terminal of the signal processing unit is connected to the output terminal of the light-free unit and the output terminal of the transimpedance amplifier. The signal processing unit detects the static voltage and the average voltage of the voltage signal, and obtains the amplified voltage based on the voltage signal and the average voltage of the voltage signal. The input terminal of the control unit is connected to the output terminal of the signal processing unit, the first output terminal of the control unit is connected to the light-free unit, and the second output terminal of the control unit is connected to the input terminal of the transimpedance amplifier; the control unit generates a control signal based on the amplified voltage. The control signal adjusts the static voltage of the light-free unit and the DC signal of the transimpedance amplifier to change the voltage signal output by the transimpedance amplifier.

2. The transimpedance amplifier output signal conditioning circuit of claim 1, wherein, The control signal includes a first regulating current and a second regulating current, wherein the first regulating current is output to the light-free unit through the first output terminal of the control unit to regulate the static voltage; The second regulating current is output to the transimpedance amplifier through the second output terminal of the control unit to eliminate DC in the current signal.

3. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 2, characterized in that, The control unit includes a first adjustment module and a second adjustment module; The first adjustment module includes a first current mirror, which is connected to the input terminal of the transimpedance amplifier and the output terminal of the signal processing unit. The first current mirror converts the amplified voltage into a first adjustment current. The second adjustment module includes a second current mirror and a current processing submodule; The second current mirror is connected to the output terminals of the light-free unit and the signal processing unit, and the second current mirror converts the amplified voltage to obtain an intermediate current.

4. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 3, characterized in that, The current processing submodule includes a first current mirror pair and a second current mirror pair; the first current mirror pair and the second current mirror pair sequentially perform polarity conversion on the intermediate current and output a second regulating current.

5. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 4, characterized in that, The first current mirror and the second current mirror have the same structure, and the component size ratio between them is M:1; the first current mirror pair and the second current mirror pair have the same structure, and the component size ratio between them is N:1, where M and N are positive integers.

6. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 5, characterized in that, The adjustment circuit also includes a differential amplifier; The inverting input of the differential amplifier is connected to the output of the transimpedance amplifier to receive the voltage signal; the non-inverting input of the differential amplifier is connected to a reference voltage; and the control terminal of the differential amplifier receives a gain control signal. The differential amplifier processes the voltage signal and the reference signal based on the gain control signal to obtain the output voltage.

7. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 6, characterized in that, The control unit also includes a third current mirror, which is connected to the output of the signal processing unit and the control terminal of the differential amplifier. The third current mirror converts the amplified voltage into a third adjustment current, which serves as the gain control signal for the differential amplifier.

8. The adjustment circuit for the output signal of the transimpedance amplifier according to claim 7, characterized in that, The first current mirror, the second current mirror, and the third current mirror are all voltage-controlled current sources.

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