Track and Hold Amplifier Investigation for 100-GHz Bandwidth, 200-GS/s ADC Front Ends
Gregory Cooke, Naftali Weiss, Peter Schvan, P. Chevalier, Andreia Cathelin, Sorin P. Voinigescu
Abstract
We report on the track and hold amplifier (THA) topology choice and design details of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> time-interleaved 200-GS/s SiGe BiCMOS ADC front end with a measured SNDR > 25 dB up to 63 GHz, and with a large signal bandwidth of 58 GHz when subsampling at 5 GS/s. We show that by replacing the current-mode-logic (CML) MOS switch with a quasi-CML switch and increasing the tail current, a THA with a measured small-signal bandwidth of 101 GHz is obtained in the same 55-nm SiGe BiCMOS technology. The ADC front end bandwidth could thus be further improved at the same sampling rate.