A Differential PD/TIA Interface for Enhanced SNR and Baseline Wander Reduction in High-Speed CMOS Optical Receivers

Abstract

In this paper, a photodiode (PD)/transimpedance (TIA) interface is presented. The cathode terminal of the PD is AC-coupled to one of the inputs of a pseudo-differential TIA while the anode terminal is DC-coupled to the other input of the TIA. The DC-coupled input provides a path for the low-frequency component of the input signal to reach the output. This component is extracted by a baseline wander compensation scheme (BWCS) and fed to the input to eliminate signal drift after long data runs. Compared with the conventional pseudo-differential receiver, the proposed interface improves the gain, the gain-bandwidth product (GBW), and the signal-to-noise ratio (SNR) by 5dB, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.37\mathrm {\times }$ </tex-math></inline-formula> and 4.5dB, respectively, while maintaining <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$209\mathrm {\times }$ </tex-math></inline-formula> smaller low cutoff frequency than the AC coupled receiver. The proposed interface is compatible with any TIA topology. Post-layout simulations and analytical models validate the feasibility of the proposed technique.