Design And Research For Preampliifer In Optical Receivers

In recent years, optical fiber communication is developing more and more rapidlyand attracts wide attention. As the key part in the optical receiver, the performance ofthe preamplifier is a comprehensive reflection of optical fiber communication system.When the optical receiver is close to the optical transmitter, the modulated signal fromthe transmitter must be weak, to prevent saturation of the circuit resulting from the highinput current, which will make the case that the circuit cannot response right to the inputcurrent and return slow to normal operating mode. When the optical receiver is far fromoptical transmitter, the modulated signal from the transmitter must be strong to preventserious decay after long distance transmission. Since the difference of emission currentand fiber length, the optical receiver must have a wide dynamic range. At the same time,the preamplifiers are commonly required to have a high gain and low input noise toamplify the weak and susceptible input signal.Therefore, this paper presents the preamplifier with high gain and wide dynamicrange using CMOS process. The three-stage cascade current reuse inverter is used toachieve the high gain. The automatic gain control is used to realize the wide dynamicrange. The bandwidth is effectively enlarged by inductive-series peaking technique.The design circuit of the preamplifier with high gain and wide dynamic range isrealized in SMIC0.18μm1P6M CMOS process. From the simulation results, thepreamplifier proposed displays a maximum transimpedance gain of88.3dB with the-3dB bandwidth of1.8GHz, exhibits an input current dynamic range from100nA to10mA. And the output voltage noise is less than48.23nV/sqrt(Hz) within the-3dBbandwidth. The design circuit dissipates a dc power of9.4mW with1.8V supply voltage.Through layout design, the layout area of the whole circuit is about800μm×750μm. Thepreamplifier with high gain and wide dynamic range is suitable for2.5Gbit/s opticalfiber communication.