Optimization And Design Of Optical Receiver Analog Front End Circuit Of RGC Configuration

With the rapid development of information technology,the requirements of high speed communication increased continuously.Up to now,optical communication has been applied to optical interconnection system.As one of key modules in optical communication system,although the optical receivers integrated by hybrid mode have achieved much progress,there are still many problems need to be solved,such as large volume,high cost,and poor reliability.Therefore,the monolithically integrated optoelectronic circuit incorporating photoreceptor and electronic circuit on the same silicon substrate is still a challenge.As a key module of optical receiver,the transimpedance amplifier(TIA)is a key factor limiting the performance of optical receiver,so the performance improving for TIA is still a research focus in the field of optical communication.Due to the excellent characteristics,regulated cascade(RGC)configuration used for TIA design has been studied extensively and applied in many optical receivers.Up to now,many novel structures of RGC configuration with improved performance have been developed.However,the RGC improving technology was always reported as an optimizing method for the performance enhancement of TIA,and not independent from the TIA optimizing technology.Since RGC configuration has excellent characteristics and potential possibility of improving,this paper summarized various improving technologies for RGC configuration,and analyzed their advantages and disadvantages.Based on the analysis results,two kinds of analog front-end circuit for optical receiver were proposed.The main contents are as follows:Firstly,the existing RGC improving technologies were summarized,and four types were classified.They are auxiliary amplifier improving technology,input end network matching technology,current enhancing technology,pole and zero offset technology.The structural features and performance characteristics of different RGC improving technology was also analyzed.Secondly,two kinds of novel RGC TIA were proposed base on the analysis results.The first circuit is a differential cross-coupled RGC TIA with high bandwidth.In the design,multistage CS cascade boosting the gain of auxiliary amplifier was adopted.To realize optimal frequency compensation,the shunt active inductor peaking technique was applied too.The second one is the best biased RGC TIA with high gain and low noise.Except the auxiliary amplifier improving technique and input end network matching technique,a best bias technique was proposed to make the main amplifier and auxiliary amplifier operate in optimal state.Thirdly,a limiting amplifier(LA)was improved with shunt active inductor,and two kinds of analog front-ends for optical receiver were designed optimally based on the proposed RGC TIAs and UMC 0.18 ? m CMOS process.Simulation results indicated that the front-end circuit with differential cross-coupled RGC TIA has a transimpedance gain of 81dB? and a-3dB bandwidth of 3.7GHz,and the corresponding noise current spectral density at-3dB bandwidth is 38 pA/Hz1/2.Additionally,the analog front-end with best bias RGC TIA has a transimpedance gain of 92dB? and a-3dB bandwidth of 3.7GHz,and the corresponding noise current spectral density at-3dB bandwidth is 11.4 pA/Hz1/2.the eye diagram of 5Gb/s is clear.The above results demonstrate that our designed optical receiver front-ends can operate at 5Gb/s.