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Topic: Op amp output as digital input (Read 768 times) previous topic - next topic

sreedevk

Hi,
I am planning to provide a 5V output of an op amp directly to a digital pin as input to Arduino Mega. Is there any chance of damaging the board?

johnwasser

As long as the voltage is limited to the range 0 to 5V it will not harm the Arduino.
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sreedevk

Thanks. One more question. If i supply 5V to the output pin of an op amp, will it damage the op amp?

winner10920

Depends on the opamp, if the 5v is coming from an arduino output you may fry the arduino pin first, depends onthe actual opamp, you couldn't go wrong with a 220 -1kohm resistor in between, you'll never have a problem then so long as the opamp doesn't go above 5v, and then a 5.1v zener would fix that

dhenry

Quote
If i supply 5V to the output pin of an op amp, will it damage the op amp?


Depending on the opamp, but generally no for small signal opamps and potentially yes for power opamps.

johnwasser

I suspect that if you connect the output directly to the 5V supply and the output is trying to drive LOW (0V) you will probably damage the output transistors of the op-amp.  

If you connect through a pull-up resistors you might be OK.  Depends on how much current the op-amp can source or sink and how much current will flow through your pull-up.  A 1K resistor (5 mA current) might be safe.  Depends on your op-amp.
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Grumpy_Mike

Quote
If i supply 5V to the output pin of an op amp

This begs the question as to why on earth you would want to apply a 5V power line to an output. Connecting outputs direct to a supply makes no sense. What are you trying to do?

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