An 8-bit, 12 GSample/sec SiGe track-and-hold amplifier

We present the design and implementation of an ultra-high-speed SiGe BiCMOS track-and-hold amplifier (THA) for use in high-speed analog-to-digital converters. The use of a degeneration inductor in the input buffer significantly improves the performance of the THA. The THA was fabricated in a commercially-available 0.25 /spl mu/m 200 GHz SiGe HBT BiCMOS process technology. The circuit occupies an area of 1.2 mm/sup 2/, and exhibits -49.5 dBc of total harmonic distortion (THD) when operated at a sampling frequency of 12.5 GHz with an input frequency of 3.0 GHz. Operating from a 3.5 V supply, the total power consumption is 0.7 W. To our knowledge, this circuit is the fastest 8-bit Si-based THA achieved to date.