Compact Inductor-less CMOS PAM4 VCSEL Driver for High-speed Optical Communications

A compact VCSEL driver circuit supporting PAM4 signals for high-speed communications is proposed. The proposed circuit achieves a wide bandwidth with active inductors that can supply a large amplitude voltage and an active feedback that applies strong negative feedback. The active inductor with level shift enhances high linearity in the output signal by overcoming limitations of the circuit bias conditions. This configuration without spiral inductors reduces the circuit area by 49 % compared to the circuit designed with inductive shunt peaking. The proposed circuit was fabricated in 0.18-μm CMOS technology. It operates at a bit rate of 6 Gb/s, consumes 124.2 mW, and occupies an integrated area of 0.115 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .