A CMOS infrared optical preamplifier with a variable-gain transimpedance amplifier

A CMOS infrared wireless optical receiver front-end is described. A feedback analysis is carried out for the design of a stable variable-gain transimpedance feedback amplifier. A current-mode amplifier, exhibiting a low input resistance and a high output resistance, is designed. The current amplifier is employed as the feedforward gain element of a variable-gain fully-differential transimpedance feedback amplifier. For an infrared wireless optical receiver front-end employing the transimpedance amplifier, the optical preamplifier achieves a transimpedance gain of 87dB/spl Omega/, a bandwidth of 135MHz with a 5pF photodiode capacitance, and a power consumption of 28mW.