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OpAmp related question 
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#1
Apr411, 09:18 PM

P: 5

1. The problem statement, all variables and given/known data
2. Relevant equations v_{o} = G*v_{s} where G = ((R_{1}+R_{2})/(R_{2}) therefore, v_{o} = v_{s} * ((R_{1}+R_{2})/(R_{2}) would v_{o} be independent of R_{s} ? 3. The attempt at a solution I assumed it was a Non Inverting Op Amp...but I haven't come across one with (two?) input resistances? I'm not sure where to go with it. I began to use the equation I have above, but I don't think it's right. I think (or I keep telling myself) that I have to use R_{s} or R_{x} in part a somehow. For part b) I believe I have to figure out the linear range of R_{x}, which should be doable. So I'm not worried about that, assuming what I'm thinking is correct... If anyone can help thanks! If not, thanks anyways! 


#2
Apr411, 09:23 PM

P: 2,179

One question that may help  What is the voltage at the + input of the Op Amp. Is it 750 mV, or something else?



#3
Apr411, 09:24 PM

Mentor
P: 12,069

EDIT: phyzguy had the same thought. 


#4
Apr411, 09:26 PM

P: 5

OpAmp related question
I solved it, I had to solve for a noninverting (positive) input voltage (v_{p}) first and then created a "new" circuit. Using that circuit I found the output voltage using that equation I listed above while replacing v_{s} with v_{p} .
I got v_{p} = [(80k/(80k+20k)]*750 mV = 600 mV then v_{o} = [(3.3k+46.2k)/3.3k]*600 mV = 9000 mV It feels good to figure my own answer out...lol EDIT: I didnt refresh, so I didn't see your guys replies. Thanks all! :) 


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