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How to calculate op amp output voltage?

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Blue10

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Hello everyone,
Please help me find the output voltage formula for this operational amplifier circuit.
opamp.png

Thank you.
 

Hi,

R1 is useless.

Klaus
 
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    Blue10

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Hi,

I've just seen the schematic ...
you have a simulation tool. Why don't you try it? ;-)

Klaus
 
If the op-amp is ideal (or close to be ideal), in the linear range the voltage at the inverting input equals the voltage at the non-inverting input so R1 is short-circuited by the behavior of the op-amp itself.
 
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albbg said:
If the op-amp is ideal (or close to be ideal), in the linear range the voltage at the inverting input equals the voltage at the non-inverting input so R1 is short-circuited by the behavior of the op-amp itself.
Click to expand...
I know and realize that - as it seems - the question comes from a beginner.
And - as far as an idealized opamp is concerned - I agree to your answer.

However, for real opamps with a frequency-dependent gain the resistor R1 is NOT useless. It resembles a special kind of external frequency compensation - thereby improving the phase margin as well as the step response. More than that, using such a resistor across the opamps input nodes allows us to use opamps which are not unity-gain stable even with 100% feedback (unity gain).
 
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Hi,

I agree. But I doubt that's the OP's question, or can gain some help from this information.

Klaus
 
KlausST said:
Hi,
I agree. But I doubt that's the OP's question, or can gain some help from this information.
Klaus
Click to expand...
OK - I agree.
On the other hand, if I read something that is not quite correct, can it then be a mistake to correct or complete it?
Maybe it is a good hint - even for the beginner - that circuits can behave completely different under real conditions if compared with idealized models.
 
Hi,

No, please keep on correcting mistakes. We (the forum) don't want to spread mistakes.
I'm not free of mistakes - and I'm curious to learn new things every day.
So, everything is fine. I can stand being corrected.

Klaus
 

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