A 10-b, 1-GSample/s track-and-hold amplifier using SiGe BiCMOS technology

An open-loop pseudo differential BiCMOS track-and-hold amplifier (THA) employs a new adaptive-biased input buffer to maintain performance at high input frequencies. An auxiliary THA undergoes all linearity-degrading loading impacts to generate compensating signals. These signals are exploited to improve the hold-mode suppression in the main THA. Designed total harmonic distortion (THD) is -63.7 dB at Nyquist condition, f/sub in/=500 MHz, with full-scale differential input swing of 1 V. Fabricated in a 0.5 /spl mu/m, 40 GHz BiCMOS process, the THA core consumes 164 mW from a 3.5 V power supply and occupies an active area of 1 mm/sup 2/. The hold-mode feed through measures -54 dB at f/sub in/=93.75 MHz and the droop rate is -0.33 /spl mu/V/nS.