Low-noise transimpedance amplifier designg procedure for optical communications

Here, we report on design and measurement results of a state of the art low-noise and high-gain transimpedance amplifier (TIA) implemented in 0.18 μm TSMC CMOS technology. In depth design methodology for design of high gain and low noise TIA for 2.5 Gb/s optical communication family is presented. A novel noiseless capacitive feedback is proposed and implemented as a noise efficient feedback for TIA circuits. Besides, analytical noise calculations in this family of TIA circuits are presented and optimum noise criteria are derived. The saturation and instability problem of TIA circuits resulted from DC dark current of the input photodiodes (PDs) is addressed and a circuit-level solution is proposed. The measurement results of 0.18 μm chip shows bandwidth of 52 kHz to 1.62 GHz, and transimpedance gain of 75.5 dBΩ while dissipating 26.3 mW from a 2.2 V power supply, including the output buffer. Taking advantage of proposed capacitive feedback network and optimum noise criteria, noise measurement results show average input referred current noise of 3.18 pA/√Hz for this TIA in the bandwidth of operation.