155 Mb/s automatic gain control CMOS transimpedance preamplifier for optical communication

A transimpedance preamplifier with automatic gain control (AGC) for 155 Mb/s optic-fiber communication was designed and realized in CSMC 0.6 μm standard CMOS technology. For the extension of input dynamic range, uses automatic gain control technique to monitor the variation of input dc component which is proportional to the magnitude of input current. When input current is large, transimpedance gain decreases to avoid output distortion. After analyzing contributions to equivalent input noise current of several elements in the circuit, gives a method of noise performance optimization. The measured results show that the pre-amplifier has differential transimpedance of 91.7 dBΩ (38.5 kΩ), -3 dB bandwidth of 125 MHz, optical overload of 0 dBm and average equivalent input noise current density of 4.8 pA. Its power consumption is 180 mW under single 5 V power supply and the die area is 0.7 × 0.4 mm².