A transimpedance preamplifier with automatic gain control (AGC) for 155Mb/s optic-fiber communication was designed and realized in CSMC 0.6 μ m 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 91.7dB Ω (38.5k Ω )

-3dB bandwidth of 125MHz

optical overload of 0dBm and average equivalent

input noise current density of 4.8pA.Its power consumption is 180mW under single 5V power supply and the die area is 0.7×0.4mm

2

.