Find Vout for Op-Amp Circuit with Attached Image

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Discussion Overview

The discussion revolves around finding the output voltage (Vout) for an operational amplifier (op-amp) circuit, as depicted in an attached image. Participants explore the theoretical aspects of the circuit configuration and its implications on the output voltage.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant notes that since Vb is grounded, it is equal to 0, which leads to the conclusion that Va must also be 0 based on op-amp rules.
  • The same participant formulates a node equation at Va, resulting in -Vin/R1 - Vout/R2 = 0, and calculates Vout as -5V using given values.
  • Another participant confirms that -5V is correct, describing the circuit as an "inverter".
  • A third participant suggests rearranging the equation to express the gain as Vout/Vin = -R2/R1, indicating that if R2 equals R1, the gain would be -1.

Areas of Agreement / Disagreement

There is agreement on the calculation of Vout as -5V, but the discussion includes varying levels of detail regarding the gain and configuration of the circuit, indicating that multiple perspectives are present.

Contextual Notes

The discussion does not resolve the implications of varying resistor values on the gain or the broader context of the circuit's application.

Who May Find This Useful

This discussion may be useful for individuals interested in operational amplifier circuits, circuit analysis, and the mathematical relationships governing gain in electronic systems.

Metamorphose
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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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