A 25Gbps Single-Ended to Differential Low-Noise Transimpedance Amplifier in 45nm SOI for High-Speed Optical Transceivers

Abstract

High-speed optical transceivers are advancing towards lower noise and power consumption, necessitating enhanced transimpedance amplifier (TIA) designs. This paper presents a 25Gbps single-ended to differential (S2D) low-noise TIA implemented in 45nm SOI technology. The design utilizes AC-coupling capacitors and a cross-coupled capacitor pair to achieve differential output. To optimize noise and bandwidth performance, a high-gain, low-bandwidth input stage is followed by a continuous-time linear equalizer (CTLE). The CTLE incorporates inductive peaking and negative capacitance techniques, achieving a bandwidth extension ratio (BWER) of 3.9 with less than 0.5dB peaking. Post-simulation results demonstrate the TIA achieves a transimpedance gain of 57.1 dB and a bandwidth of 23.7 GHz, considering a photodiode capacitance of 70fF. The input average noise current spectral density is 10.9 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$pA/\sqrt{Hz}$</tex>, with a power consumption of 38mW at a 1.3V supply voltage.