A 40 GS/s SiGe track-and-hold amplifier

An ultra-high-speed SiGe track-and-hold amplifier (THA) using a switched-emitter-follower (SEF) configuration is presented. Operating off a +5.5 V power supply, this THA exhibits -32.4 dBc of total harmonic distortion (THD) when sampling a 10 GHz input signal at the rate of 40 GS/s, and reaches -50.5 dBc of THD when sampling a 2 GHz input at 12 GS/s. Compared to the THAs published in the literature with an operational range from 10 GS/s to 20 GS/s, the present THA demonstrates a THD comparable to the best one achieved to date to our knowledge for Si technology, with much improved high-frequency characteristics. On the other hand, in the operational range of 30 GS/s and above, the present SiGe THA still exhibits robust characteristics compared to the fastest THAs in terms of linearity, power consumption, and sampling rate.