What's Wrong with an Op Amp Used as a Voltage Comparator?

I use a voltage comparator to make an amplifier circuit, but something went wrong. Someone showed me an lm393 amplifying circuit, the magnification is 2. It is related with the idea of "When the frequency requirement is not high, the operational amplifier can also be used as a low-performance comparator in practical applications.
In theory, an operational amplifier with an open-loop configuration (no negative feedback) can function as a low-end comparator."(source from https://www.apogeeweb.net/electron/using-op-amp-as-comparator.html)

Is there anyone can give me some advice? Many thanks.

qrk2020-08-21T18:00:10Z

The article is right. You can use an opamp for a comparator, but it is slow because it takes time for an opamp to come out of saturation. Comparators don't have this issue. Opamps don't come in open-collector/drain configurations, comparators do. Generally, when I use a comparator, I need something to happen in under 30ns which rules out using an opamp.

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