Difference between Op Amp and Comparator

Operational amplifiers and comparators are exactly the same. Simply put, comparators are open-loop applications of op amps, but comparators are designed for voltage threshold comparisons, requiring precise comparison thresholds, short output edge rise or fall times after comparison, and outputs that comply with TTL/CMOS levels/or OC, etc., without requiring accuracy in the intermediate links, and different driving capabilities. In general, when op amps are used as comparators, most cannot achieve full-scale output, or the edge time after comparison is too long, so it is better to use fewer op amps as comparators in designs.

Difference between Op Amp and Comparator

Although comparators and op amps have the same symbols on the circuit diagram, there are very big differences between these two devices and they are generally not interchangeable. The differences are as follows:

1. The comparator has a fast flipping speed, which is about the order of ns, while the op amp flipping speed is generally on the order of us (except for special high-speed op amps).

2. The op amp can be connected to the negative feedback circuit, but the comparator cannot use negative feedback. Although the comparator also has two input terminals, the in-phase and inverting input terminals, it does not have a phase compensation circuit inside. Therefore, if negative feedback is connected, the circuit cannot work stably. There is no internal phase compensation circuit, which is also the main reason why the comparator is much faster than the op amp.

3. The output stage of the op amp generally adopts a push-pull circuit and a bipolar output. However, the output stage of most comparators is an open collector structure, so a pull-up resistor is required, and the unipolar output is easy to connect to digital circuits.