High level resolution enhancement for dual-range A/D conversion

Claim 1

A dual range analog-to-digital converter for converting analog input signals into digital output signals, the digital signals having code values corresponding to the analog levels of the input signals, said converter comprising: a first signal path including a first analog-to-digital converter for converting the analog input signals into first digital signals; a second signal path including a second analog-to-digital converter for converting the analog input signals into second digital signals; amplification means for providing signal gain in the respective signal paths, the gain applied to the second path being a nominal multiple of the gain applied to the first path; multiplexing means responsive to the the signals in the respective signal paths for generating the digital output signals from either the first signal path or the second signal path; means for appending a predetermined number N of random noise bits as the N least significant bits of the first digital signals, and means for adding N bits of a predetermined value to the N most significant bits of the digital signal in said second path.