A 1.93 pA/√Hz transimpedance amplifier for 2.5 Gb/s optical communications

A state-of-the-art low-noise transimpedance amplifier (TIA) for 2.5 Gb/s family is presented using IBM 0.13-μm CMOS technology. This TIA would be a pa rt of a homodyne detector in a quantum key distribution (QKD) system. In this work a thorough design methodology based on a novel analytical noise optimization is presented. Also a unique method for eliminating the DC current o f the input photodiodes (PDs) is proposed. The post-layout simulation results show bandwidth of 52 kHz to 1.9 GHz, average input referred noise of 1.93 pA/√(Hz), and transimpedance gain of 80 dbΩ while dissipating 12 mW from a 1.5 V power supply, including the output buffer.