Fast rail-to-rail voltage comparator and method for rail-to-rail voltage comparison

摘要

Method and apparatus are provided for fast rail-to-rail voltage comparison. A rail-to-rail voltage comparator for indicating one of two states with an output signal in response to an input signal is provided comprising an input stage having an input configured to receive the input signal and having an output, and an amplification circuit having an input coupled to the output of the input stage. The input stage comprises a first differential amplifier having a first input-voltage range and configured to produce a first current based on the input signal, a second differential amplifier having a second input-voltage range and configured to produce a second current based on the input signal, and a summing circuit having a first input coupled to the first differential amplifier and having a second input coupled to the second differential amplifier. The first input-voltage range overlaps the second input-voltage range. The summing circuit is configured to produce a first voltage at the output of the input stage based on a sum of the first current and the second current. The amplification circuit is configured to incrementally amplify the first voltage to a second voltage and further configured to produce the output signal having the second voltage. The second voltage indicates one of the two states.