A CMOS voltage comparator

Abstract

A CMOS voltage comparator, comprising: a multistage amplifier, the first output terminal of each stage amplifier is connected to the first input terminal through a switch, the second output terminal is connected to the second input terminal through a switch, and the two switches are connected simultaneously Open or closed; the input terminal of each stage amplifier is connected to the output terminal of the previous stage amplifier, and the switches of all amplifiers are opened or closed at the same time; double-ended input to single-ended output conversion circuit, the input terminal is connected to the output terminal of the last stage amplifier Connected; multi-stage output shaping circuit, the input end is connected to the output end of the double-ended input to single-ended output conversion circuit; the DC blocking capacitor is located before the amplifiers of all levels and the input end of the double-ended input to single-ended output conversion circuit; the first The switch, the input signal is connected to the first-stage amplifier after passing through the first switch and the DC blocking capacitor; the second switch, the input signal is grounded after passing through the second switch, and the second switch is opened or closed simultaneously with all switches of the multi-stage amplifier.

Description

technical field [0001] The invention relates to a voltage comparator, in particular to a CMOS voltage comparator composed of multi-level circuits. Background technique [0002] In the traditional comparator in the integrated circuit, the operational amplifier is usually used as the comparator, and the comparison function is realized by utilizing the characteristic of the large open-loop gain of the operational amplifier. If the input voltage of the positive terminal is higher than that of the negative terminal, the output will be a high level; if the input voltage of the positive terminal is lower than that of the negative terminal, a low level will be output. In this way, the comparison of the input voltage at the positive and negative input terminals is realized. The functional block diagram and working principle diagram of the circuit are shown in figure 1 as shown, figure 1 (a) is a functional block diagram, figure 1 (b) is the working principle diagram, in which the...

AI Technical Summary

Problems solved by technology

[0003] Due to the existence of the offset voltage of the op amp, it will affect the accuracy of the comparator

And because the open-loop gain of the op amp is very large, a small offset voltage may cause the circuit to saturate

thus not working properly

[0004] Due to the lack of positive feedback, the speed of the comparator is limited by the slew rate (SLEW RATE) of the op amp. Due to the use of a single-stage op amp, the switching speed is very slow, resulting in a very slow slew rate.

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