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  • How to distinguish between amplifiers and comparators?

    * Question

    How to distinguish between amplifiers and comparators?


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    Answer

    The difference between the op amp and the comparator: Although the comparator and the op amp have the same symbol on the circuit diagram, the two devices do have a very big difference, and generally cannot be interchanged. The difference is as follows:

    1. The flipping speed of the comparator is fast.It is on the order of ns, and the op amp flip speed is typically on the order of us (except for special high-speed op amps).There is no phase compensation circuit inside, which is the main reason why the comparator is much faster than the op amp.3. The output stage of the op amp generally uses a push-pull circuit and a bipolar output.Most comparator output stages are open-collector structures, so pull-up Resistorss, unipolar outputs, and easy connection to digital circuits are required.Used as an amplifier. Because the comparator is optimized for speed, this optimization reduces the range of closed-loop stability. The op amp is optimized for the closed-loop stability range, so the speed is reduced. So the comparators of the same price grade andThe amplifier is best responsible for each other. Just as the amplifier can be used as a comparator, the ratio cannot be excluded.Check to ensure stability in all working conditions of the product! At this time you have to carefully calculate the cost/risk.

    2. The amplifier and comparator are exactly the same. In a nutshell, the comparator is the open-loop application of the op amp.However, the comparator design is for voltage threshold comparison, and the required comparison threshold is accurate.General situation: When using an op amp as a comparator, most of them do not reach the full-scale output, or the edge time after comparison is too long. Therefore, it is better to use the op amp as a comparator in the design.


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