A 25-GSa/s InP DHBT Track-and-Hold Amplifier Using Active Peaking Input Buffer

In this letter, we present a 25-GSa/s wideband track-and-hold amplifier using 0.8-
${\mu }\text{m}$
indium phosphide (InP) process for high-speed analog sampling front-end. In this design, an active peaking input buffer is first used in the base–collector switching diode sampler. Moreover, it is carefully calculated and analyzed. The dominant pole in the signal path of the circuit is canceled by one zero produced by the active peaking structure; therefore, the bandwidth (BW) is extended. The experimental results show that a total harmonic distortion (THD) of less than −27 dBc and a spurious-free dynamic range (SFDR) of better than 32.5 dB are demonstrated at a 25-GSa/s sampling rate. In the hold mode, the isolation is better than −42 dB. In addition, it has an 0.156
${f_{T}}$
BW from dc to 25 GHz within 160-GHz
${f_{T}}$
, which is a very competitive value compared with other reported track-and-hold amplifiers (THAs) using the InP process.