Design And Simulation Of The Pre-amplifier For2.5Gbps CMOS Optical Receiver

With the development of science and technology and the progress of the society,the amount of information is also increasing continuously; the requirements to thespeed in the information processing of people’s are also higher and higher, so thesegive the communication system much more strict requirements. During these years,optical fiber communication system, with great advantages of its capacity, loss andsecurity, has got very fast development. Especially, the problem of how to use thestandard CMOS technology to integrate the high-speed optical fiber transmissionsystem has become the hot topic of the research in the world today.In the optical fiber transmission system, the optical receiver system is anindispensable component, and the module of pre-amplifier is an important part of theoptical receiver system. Therefore, this paper makes some research about the opticalreceiver pre-amplifier based on the standard CMOS technology, and designs atransimpedance pre-amplifier with wider bandwidth which can be used for2.5Gbpstransmission system. At the same time, this paper increases the amplifier gain as largeas possible after the requirement of wide bandwidth is met.The optical receiver pre-amplifier circuit designed in this paper mainly includesthree parts such as the RGC transimpedance amplifier, single-ended output todifferential output module and the AGC circuit. Among them, the RGCtransimpedance amplifier module is mainly responsible for converting the currentpulse signal into a voltage signal and amplifying it properly which can be used by thelater circuit. In order to isolate the parasitic capacitance of the photo-electric detectorfrom influencing the amplifier, the RGC is added to the circuit as the input buffer levelof the amplifier. In order to further improve the bandwidth of the circuit, thetechnology of active inductor peaking is also used in the circuit, at the same time, thesource follower is added to isolate the big amplifier output impedance from influencingthe feedback resistance. The single-ended output to differential input module is mainlyresponsible for converting the single-ended output signal into the differential inputsignal which can be suitable for the amplifier circuit later. In order to further expandthe bandwidth, the capacitive degradation technology is introduced, at the same time, aoutput buffer level which has a level of50Ω impedance matching after the single-ended output to differential input circuit is added to have a good impedancematching with the other circuit out of the chip. The AGC circuit module is mainlyresponsible for controlling the output signal range to be adjustable and making theoutput voltage signal amplitude to be constant. The simulation results have showed thatthe bandwidth of the transimpedance amplifier is2.34GHz, and the gain is up to75.6dBΩ, at the same time, the equivalent noise current spectral density is only9.68pA/sqrt(Hz).Finally, this paper introduces some rules and skills and some factors need to beconsidered in the layout design, and the final layout of the circuit is showed at the endof this paper.