Rail-to-rail input hysteresis comparator

摘要

A rail-to-rail input hysteresis comparator includes: an input hysteresis comparator module, a transmission module, an output comparator, a switching signal module and a bias module. Compared to the conventional device, the rail-to-rail input hysteresis comparator of the present invention can turn off an output of the N-type input hysteresis comparator of the input hysteresis comparator module when the common mode input voltage is relatively low and turn off an output of the P-type input hysteresis comparator of the input hysteresis comparator module when the common mode input voltage is relatively high, thereby avoiding operating in a linear mode and hence achieving a stable CMRR.

主权项

1. A rail-to-rail input hysteresis comparator, comprising an input hysteresis comparator module, a transmission module, an output comparator, a switching signal module and a bias module, wherein:
the input hysteresis comparator module comprises a P-type input hysteresis comparator and an N-type input hysteresis comparator, the P-type input hysteresis comparator having a first input terminal, a second input terminal, a first output terminal, a second output terminal and a P-type common mode voltage control signal output terminal, the N-type input hysteresis comparator having a first input terminal, a second input terminal, a first output terminal, a second output terminal and an N-type common mode voltage control signal output terminal, the input hysteresis comparator module configured to receive a P-type input signal and an N-type input signal and to output a P-type hysteresis signal and an N-type hysteresis signal, each with hysteresis and steeper rise and fall edges relative to a respective one of the P-type input signal and the N-type input signal, to the transmission module and simultaneously a P-type common mode voltage control signal and an N-type common mode voltage control signal; the switching signal module is configured to convert the P-type and N-type common mode voltage control signals output from the input hysteresis comparator module to switching signals for the transmission module; the output comparator comprises a P-type comparator and an N-type comparator, both coupled to the transmission module; the transmission module selectively couples one of the P-type and N-type hysteresis signals to the output comparator, under control of the switching signals, such that when the input P-type common mode voltage control signal is as low as to cause a decrease in a common mode rejection ratio, an output of the N-type input hysteresis comparator of the input hysteresis comparator module is disabled and an input voltage of the P-type comparator of the output comparator is set to a high level, thereby rendering the P-type comparator of the output comparator out of operation, and when the input N-type common mode voltage control signal is as high as to cause a decrease in the common mode rejection ratio, an output of the P-type input hysteresis comparator of the input hysteresis comparator module is disabled and an input voltage of the N-type comparator of the output comparator is set to a low level, thereby rendering the N-type comparator of the output comparator out of operation; and the bias module is configured to generate a bias current and a bias voltage, for each of the input hysteresis comparator module, the transmission module, the output comparator and the switching signal module.