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Automatic gain control circuit and method of transimpedance amplifier circuit

An automatic gain control and transimpedance amplifier technology, applied in the field of optoelectronic communication, can solve the problems such as the inability of the transimpedance gain to remain stable, the long convergence time of the automatic gain control loop, and the jitter of the output signal, so as to improve the input dynamic range and widen the dynamic range. Good scope and scalability

Pending Publication Date: 2021-11-16
HENGXIN SEMITECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

On the one hand, if 1 / (RC) is too large, the low-frequency AC component in the data signal will not be attenuated by the low-pass filter, so that the transimpedance gain cannot be kept stable, resulting in output signal jitter; on the other hand, a large RC Determines that the automatic gain control loop needs a long convergence time to establish a steady state
Therefore, this automatic gain control method is only suitable for continuous communication mode

Method used

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  • Automatic gain control circuit and method of transimpedance amplifier circuit
  • Automatic gain control circuit and method of transimpedance amplifier circuit
  • Automatic gain control circuit and method of transimpedance amplifier circuit

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Embodiment 1

[0038] refer to figure 1 , the embodiment of the present invention provides an automatic gain control circuit of a transimpedance amplifier circuit, on the basis of Embodiment 1, wherein, refer to image 3 , transimpedance amplifier circuit, including gm amplifier tube Q1, cascode tube Q2, load circuit R load , emitter follower Q3, emitter follower bias current source I 0 , Feedback resistor R feedback , input bias resistor R sink . where the feedback resistor R feedback A resistor Rf0, a resistor Rf1, and a switch S connected in parallel with the resistor Rf1 1 Composition; input bias resistor R sink It consists of a resistor Rs0, a resistor Rs1, and a switch S1 connected in parallel with the resistor Rs1. R feedback and R sink Switch S in 1 It can be realized by a transmission gate composed of NMOS or NMOS and PMOS in parallel.

[0039] image 3 In the transimpedance amplifier circuit, the Input voltage at the input terminal is clamped at the V of Q1 be , flows...

Embodiment 2

[0046] refer to figure 1 , the embodiment of the present invention provides an automatic gain control circuit of a transimpedance amplifier circuit, on the basis of Embodiment 1, wherein, refer to Figure 4 , transimpedance amplifier circuit, and increase the second reference voltage generation circuit, input current I d2 , latching comparator and output digital control bit SW 2 , which can widen the dynamic range. Hypothesis I d1 d2 , the threshold current for gain control switching of the transimpedance amplifier is N×I d1 , N×I d2 . When I PD d1 , the digital control bit output by the first latch comparator is low level SW 1 =0, the digital control bit output by the second latch comparator is low level SW 2 =0, the feedback resistor R feedback The resistance is Rf0+Rf1+Rf2, the input bias resistor R sink The resistance is Rs0+Rs1+Rs2; when I d1 ≤I PD d2 , the digital control bit output by the first latch comparator is high level SW 1 =1, the digital control bi...

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Abstract

The invention discloses an automatic gain control circuit and method of a transimpedance amplifier circuit. The automatic gain control circuit comprises the transimpedance amplifier circuit, a reference voltage generation circuit and a resistance control circuit; the transimpedance amplifier circuit comprises an input bias resistor circuit, a forward amplifier and a feedback resistor circuit; the reference voltage generating circuit is correspondingly scaled according to the proportion of the transimpedance amplifier circuit and is used for outputting a reference voltage; the resistance control circuit comprises a low-pass filter circuit and a latch comparator, the output voltage of the trans-impedance amplifier passes through the low-pass filter circuit and is compared with the reference voltage through the latch comparator, and the latch comparator generates a digital control bit according to a comparison result, and adjusts the resistance values of the feedback resistance circuit and the input bias resistance circuit through the digital control bit, so the automatic gain control of the trans-impedance amplifier is realized. According to the invention, the dependency relationship between the maximum input current and the feedback resistance is weakened, and the input dynamic range is effectively enlarged.

Description

technical field [0001] The invention relates to the field of photoelectric communication, in particular to an automatic gain control circuit and method for a transimpedance amplifier circuit. Background technique [0002] In an optical communication system, the transmitting end emits a modulated optical signal for transmission in the optical fiber, and the photodetector (PD) at the receiving end converts the optical signal in the optical fiber into a current signal; the transimpedance amplifier is responsible for the first-level device in the electrical signal domain of the receiving end. Convert the current signal output by the photodetector into a voltage signal and provide it to the subsequent circuit. [0003] Since the optical power emitted by the laser (LD) at the transmitting end, the attenuation of the optical signal by the optical fiber, and the transmission distance are different in different links, the light intensity transmitted to the receiving end varies greatl...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03G3/30
CPCH03G3/3084
Inventor 张吉利甄治凯周俊
Owner HENGXIN SEMITECH CO LTD
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