We often use op amps to amplify weak voltage signals. Common op amps include LM358 and NE5532 instrument dedicated op amp ad620. The voltage comparator is used to compare the magnitude of the two input voltages. Common models include the LM393 dual voltage comparator and the LM339 four voltage comparator. It is widely used in circuits.

lm339 voltage comparator: Op amp and voltage comparator have the same differential input. But their output form is different, the output in the op amp uses push-pull form.

In actual use, the operational amplifier can replace the voltage comparator for voltage comparison, and the voltage comparator cannot amplify weak voltage signals. For example, when we use a current transformer to measure current, we need to use an operational amplifier to amplify the weak current signal and use a single-chip microcomputer to collect it. In the leakage switch, a voltage comparator is used. When the zero-sequence transformer detects the current and reaches a certain value, the voltage comparator outputs a high level, and the trip unit is controlled to complete the power-off operation.

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