A 0.2–18 GHz Schmitt Trigger with up to 13%–85% Duty-Cycle Tuning in 130nm SiGe BiCMOS

This paper reports on the design of a Schmitt trigger for the generation of high-speed switching signals with pulse-width modulation capability. The circuit is implemented using HBT transistors in a 130nm SiGe BiCMOS process, and shows broadband operation from 200 MHz up to 18 GHz. It has a single-ended output voltage swing of 400 mV, and rise/fall times of 10 ps and 13 ps at 10 GHz. The output-waveform duty cycle is tuned by varying the circuit’s threshold levels for the switching transitions, resulting in a continuous tuning range between 13% and 85% at 1 GHz. A push-pull Totem-Pole output buffer is designed to enable measurements with 50 Ω measurement equipment. The trigger circuit has 24.6 mW power consumption, in addition to 20.8 mW for the output buffer at the 50% duty cycle setting. The circuit implementation is very compact, requiring only 0.02 mm
²
of active area. To the best knowledge of the authors, this is by far the fastest reported Schmitt trigger to date.