High speed, wide dynamic range analog-to-digital conversion

Claim 1

An analog-to-digital conversion system for outputting an N bit word, comprising, an input for receiving an analog input signal, a pair of two's complement analog-to-digital converters, one being a higher range converter and the other being a lower range converter, each converter having a resolution of K bits where K is a number which is smaller than N, a unit gain path between said input and said higher range converter, amplification means between said input and said lower range converter, said amplification means having a gain equal to the desired ratio of the full-scale ranges of said two converters, means for selecting said higher range converter when there are more than N-2(N-K) significant bits in its output and for otherwise selecting said lower range converter, and, means for providing an N bit output word which is comprised of the output bits of said selected converter and N-K higher output bits having the same level as the most significant bit of said lower range converter when said lower range converter is said selected converter, and which is comprised of the output bits of said selected converter and N-K lower output bits having a zero level when said higher range converter is said selected converter.