Find Vout for Op-Amp Circuit with Attached Image

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The discussion focuses on determining the output voltage (Vout) for an op-amp circuit based on the provided image. The user correctly identifies that with Vb grounded, both Va and Vb are equal to 0. They derive the equation for node Va, simplifying it to -Vin/R1 - Vout/R2 = 0, which leads to a calculated Vout of -5V. This output is confirmed as correct, indicating the circuit functions as an inverter with a gain of -1 when R2 equals R1. The conversation highlights the importance of understanding op-amp configurations and their implications on voltage gain.
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1. Please refer to attached image.



2. The attempt at a solution.

I noted that Vb was grounded and would therefore be equal to 0 and because one of the two op-amp rules states that Va = Vb, both will be equal to 0.

I wrote an equation at node Va:

[Va - Vin]/R1 + [Va - Vout]/R2 = 0

Because Va is 0, the equation simply became:

-Vin/R1 - Vout/R2 = 0

And plugging in the given values for part (a), I acquired - 5V. I'm not sure if this is correct or not as the book does not have a solution manual available yet.
 

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-5V is right. In this configuration, the circuit is an "inverter".
 
Thanks! I was just wondering :)
 
Just for completeness...

Take your equation...

-Vin/R1 - Vout/R2 = 0

then rearrange it to give..

Vout/Vin = -R2/R1

where Vout/Vin is known as the Gain.

a) R2 = R1 so Gain = -1
b) etc
 

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