A 6-bit/200-MHz full Nyquist A/D converter

This paper deals with the development of an extremely fast 6-bit flash A/D converter. To gain insight into the nature of speed limitations, the effects arising from operation at very high sampling rates have been investigated. This led to the implementation of an optimized double-stage comparator circuit. The chip has been fabricated in a fast standard oxide isolated bipolar process. At a sampling rate of 200 MHz, measurements show excellent dynamic performance (high signal-to-noise ratio, no error codes) up to input frequencies of 100 MHz.