Parallel-serial analog to digital converters

Abstract

In an analog to digital converter in which each sampled portion of an incoming video or other analog signal is converted to a digital character in a plurality of parallel conversions occurring serially; the range of the voltage level reference signals of descending magnitude which are applied to comparators for effecting a relatively fine parallel conversion of a sampled analog signal is selected to be larger than, and offset in respect, to the steps or increments of the voltage level reference signals of descending magnitude which are applied to comparators for effecting a preceding relatively coarser parallel conversion, and the encoded outputs from the serially occurring parallel conversions are digitally added with the least significant bit of the encoded output from each preceding relatively coarser parallel conversion being accorded the same weight as the most significant bit of the encoded output from the next following relatively finer parallel conversion so as to eliminate from the result of the digital addition defects that would otherwise arise from inaccuracies in the voltage level reference signals and/or in the comparing operations of the comparators.