A high-speed 8 bit A/D converter based on a Gray-code multiple folding circuit

An A/D converter is described using a parallel structure to synthesize the multiple folding transfer characteristic for the Gray code. The number of comparators needed equals that of a purely sequential design. The performance is demonstrated by an 8 bit converter for video application, as well as a nonlinear version for PCM speech encoding. In both designs a 4-bit multiple folding circuit is followed by a 4 bit parallel block.