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

Hardware design
March 2, 2021 by Jacobi 84

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 a 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 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

All Comments

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Casper Posted on March 2, 2021

(One input jumps between 2.2V and 2.6V, and the other output jumps between 2.8 and 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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Murray Posted on March 2, 2021

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

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Dawn Posted on March 2, 2021

It seems that your oscilloscope is in AC mode. Change it to DC and try again. I don't know how much this affects.

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