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I want to ask why LM393 can't output low level?

Hardware design
September 16, 2020 by Daisy 2030

The circuit I used is Figure 1 and the simulation is Figure 2


The design idea is that 393 is connected to a 5V voltage, the external circuit signal input is the inverting input terminal, and the voltage at the non-inverting input terminal is about 1.25V. When the external circuit detects the signal, the input voltage is about 1.36V. If no signal is detected , It is about 1.10V. Then, use a multimeter to measure the output voltage of the 393. One of the inputs jumps between 2.2V and 2.6V, and the other output jumps between 2.8 and 3.1V.


What I want to get is a low voltage input signal, input into STM32. How can I improve it?

图二

图一

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Amaya Posted on September 16, 2020

(One input jumps from 2.2V to 2.6V, and the other output jumps from 2.8 to 3.1V.) What does this mean? The description must be accurate, not vague, so that others will not be easy to understand!

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  • Daisy

    Daisy Posted on September 16, 2020

    That is, when one of the 393 comparators detects a signal input, the measured voltage is about 2.2V. When there is no signal input, the measured voltage is about 2.6V. When another comparator detects a signal input, the measured voltage is about 2.8V, when there is no signal input, the measured voltage is about 3.1V.

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Rylie Posted on September 16, 2020

If it is not affected by your external resistance, it is the difference of the chip (the difference within a chip should be small).

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