Active inductor shunt peaking in high-speed VCSEL driver design

TL;DR

This paper presents an all transistor active inductor shunt peaking structure integrated into an 8-Gbps VCSEL driver, enhancing bandwidth in a radiation-tolerant CMOS process for high-speed optical links.

Contribution

Introduction of a compact, adjustable active inductor shunt peaking structure that overcomes CMOS bandwidth limitations without using linear resistors.

Findings

Achieved 8-Gbps data rate in prototype tests

Demonstrated effective bandwidth enhancement with the active inductor

Validated design through electrical and bit error ratio tests

Abstract

An all transistor active inductor shunt peaking structure has been used in a prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation tolerant purpose. The all transistor active inductor shunt peaking is used to overcome the bandwidth limitation from the CMOS process. The peaking structure has the same peaking effect as the passive one, but takes a small area, does not need linear resistors and can overcome the process variation by adjust the peaking strength via an external control. The design has been tapped out, and the prototype has been proofed by the preliminary electrical test results and bit error ratio test results. The driver achieves 8-Gbps data rate as simulated with the peaking. We present the all transistor active inductor shunt peaking structure, simulation and test results in this paper.