A 30 Ms/s 12-bit analog-to-digital converter

The authors describe a 30-megasamples/s 12-bit analog-to-digital converter (ADC) using a subranging conversion technique. The key circuits for obtaining high accuracy at a 30-MHz conversion rate are a pipelined track-and-hold circuit and a high-speed 5-bit digital-to-analog converter. These circuit design features are presented. The ADC was fabricated on a printed-circuit board with about 500 surface mounting devices, and utilized for a precision digital oscilloscope. In a curve-fit test, effective bits of better than 10.0 were obtained with up to a 10-MHz input frequency.<>