Digitizing scope displays waveforms from dc to 20 GHz

A digitizing oscilloscope which employs fast GaAs samplers to achieve high dc stability and broad bandwidth is described. The sampler switches faster than Schottky diodes, affording a greater bandwidth than previously possible with this type of oscilloscope. The instrument has an impressive rise time of better than 178.5 ps to achieve broad bandwidth with repetitive waveforms. The oscilloscope is designed to measure even the fastest digital circuit coupling. It operates with self-triggering or with an external trigger over a + or - 2 VDC range. Its built-in time-domain reflectometry capabilities should prove useful to engineers working with high-speed digital GaAs ICs. The instrument benefits from a powerful display screen, with 501 points of horizontal resolution and 256 points of vertical resolution. Its waveform arithmetic feature encompasses addition, subtraction, inversion, and four other functions.