A single chip all-MOS 8-bit A/D converter

A new analog-to-digital (A/D) conversion technique compatible with standard single channel MOS technology is described. This technique uses a string of equal value diffused resistors and a matrix of analog switches to perform high-speed successive approximation conversion. The comparator function is realized by a chopper-type amplifier to reduce the inherently high input offset voltages of MOS differential stages. Typical performance characteristics taken from a large sample of ICs are presented; a resolution of 8 bits has been achieved with a conversion time of 20 /spl mu/s. The complete system is fabricated on a 14000 mil/SUP 2/ die. Due to its small relative size, this A/D technique has been incorporated as part of a larger CODEC system.