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Please help analyze the causes of abnormal high and low levels of the output waveform of the operational amplifier circuit?

Hardware design
8월 05, 2020 by Emerson 440

VCC = 3.3V, the input signal of pin 6 of the op amp is a 1KHz sine wave whose midpoint is VCC/2, and the PP value does not exceed VCC or below GND.

The output of pin 7 of the op amp is a 1KHz square wave, but the ratio of high to low in one cycle is not 50:50, but 40:60.

The most problematic is that the 5 pin of the op amp is also a 1KHz square wave, but the high level is .5V and the low level is 1.05V.

But according to the picture, the high level of pin 5 should be 1.81V, and the low level should be 1.48V.

Very strange, please help analyze it.

The op amp is not a comparator, but an operational amplifier.

Thank you!

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Amari 게시 날짜 August 5, 2020

Is it basically normal? It's similar to Schmitt trigger. I don't see any problems.

If you want to output a sine wave, you must connect it to negative feedback.

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Justice 게시 날짜 August 5, 2020

It is estimated that the landlord uses a single power supply

See how high and low the output of pin 7 is?

If it is not a rail-to-rail op amp, the output square wave is probably not 1:1

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Ollie 게시 날짜 August 5, 2020

The effect of increasing the capacitance is to slow down the feedback response to the output.

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