The design of 8-Gbps VCSEL drivers for ATLAS liquid Argon calorimeter upgrade

We present designs and preliminary test results of LOCld1 and LOCld4, VCSEL drivers in a commercial 0.25- mu m Silicon-on-Sapphire (SoS) CMOS process for ATLAS liquid Argon calorimeter upgrade. Active shunt peaking, multiple-stage amplification and higher voltage supply are used to achieve the data rate of 8 Gbps. LOCld1 is a single channel VCSEL driver with a differential output, while LOCld4 has four channels with single-ended open-drain outputs. Both drivers have tunable modulation and peaking strength. Bias current for VCSEL is also embedded.