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Non Inverting Op-Amp Circuit Analysis

1. The problem statement, all variables and given/known data
For an input potential (Vin ) which is a 1V (peak) sinusoidal source. Calculate V1 and Vout
upload_2014-11-6_14-49-48.png

2. Relevant equations
- The laws for an op-amp
- NVM

3. The attempt at a solution
Here is my attempt not sure if correct.
upload_2014-11-6_15-2-34.png
 

Attachments

NascentOxygen

Mentor
9,159
1,021
VB = VA otherwise the OP-AMP is not operating as an amplifier. Fix this and you should be right.

This is a non-inverting amplifier, the input being applied to the (+) input.
 
VB = VA otherwise the OP-AMP is not operating as an amplifier. Fix this and you should be right.

This is a non-inverting amplifier, the input being applied to the (+) input.
Cool, just wondering why it is a negative terminal ?
 

NascentOxygen

Mentor
9,159
1,021
On diagram it has (-) for non inverting input.
(-) is the inverting input of the OP-AMP, used here for negative feedback of some output to reduce the gain from its high open-loop value. The circuit's voltage input is applied to the (+) non-inverting input of the OP-AMP.
 

donpacino

Gold Member
1,439
282
in addition to Nascent's points, you did some math solving for Vb incorrectly.
you say V1-Vb=0

so that means V1=Vb
why invert Vb?
 

psparky

Gold Member
884
32
Dont worry so much about what terminal is negative and so forth assuming this is an ideal amp.
To master op amps just stick to nodal analysis.
In this case, V1=A=B. They are all the same voltage.
We know that no current enters the op amp thru the + and - terminals.
Therefore we can easily find the voltage at A or V1 by using a simple voltage divdier. Vin X (10K/57K) = A
Now you know the voltage at B since the + and - terminals are equal in ideal amps.
Now use nodal analysis, (B / 1k) + (B - Vout)/ 10K = 0.
Solve and you are done.
 

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