The 1 GSPS digitizer in the HP 54111D oscilloscope

The author reviews the HP 54111D oscilloscope and describes the digitizers, which sample at up to 1 GSPS (gigasample per second) with 6 bits of resolution and greater than 1-GHz bandwidth. Four interleaved silicon bipolar 6-bit ADCs (analog/digital converters) form the heart of the acquisition system. A GaAs track-and-hold IC uses a dual rank sampling architecture as it fans out the signal to the ADCs. A GaAs clock-control IC accepts the sample clock from the timebase and generates the required track-and-hold clocks and ADC clocks for the system. Four silicon NMOS ICs each accept digital data at 250 MSPS (million samples per second) and provide a total memory depth of 8 K samples