Is Vo Independent of Rs in Non-Inverting Op-Amps?

  • Thread starter Thread starter Inept
  • Start date Start date
  • Tags Tags
    Op-amp
Click For Summary

Discussion Overview

The discussion revolves around the independence of the output voltage (vo) from the source resistance (Rs) in a non-inverting operational amplifier (op-amp) configuration. Participants explore the relationships between input voltages, resistances, and the output voltage, while addressing specific homework problems related to these concepts.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant presents the equation vo = G*vs, where G = (R1 + R2) / R2, and questions whether vo is independent of Rs.
  • Another participant asks for clarification on the voltage at the positive input of the op-amp, suggesting it may be 750 mV or another value.
  • A participant describes their process of solving for the positive input voltage (vp) first and then calculating the output voltage (vo) based on that, arriving at specific numerical results.
  • There is uncertainty expressed regarding the presence of multiple input resistances in the non-inverting op-amp configuration.

Areas of Agreement / Disagreement

The discussion includes multiple viewpoints and uncertainties, particularly regarding the role of Rs and the input voltage. No consensus is reached on whether vo is independent of Rs, and participants express differing levels of confidence in their approaches and solutions.

Contextual Notes

Participants reference specific values and configurations but do not fully resolve the implications of Rs on vo. The discussion reflects a mix of assumptions and exploratory reasoning without definitive conclusions.

Inept
Messages
5
Reaction score
0

Homework Statement



npi9za.png



Homework Equations



vo = G*vs

where G = ((R1+R2)/(R2)

therefore,
vo = vs * ((R1+R2)/(R2)

would vo be independent of Rs ?

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 Rs or Rx in part a somehow.

For part b) I believe I have to figure out the linear range of Rx, 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!
 
Physics news on Phys.org
One question that may help - What is the voltage at the + input of the Op Amp. Is it 750 mV, or something else?
 
Inept said:

Homework Statement



npi9za.png

Homework Equations



vo = G*vs

where G = ((R1+R2)/(R2)

therefore,
vo = vs * ((R1+R2)/(R2)

would vo be independent of Rs ?

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 Rs or Rx in part a somehow.

For part b) I believe I have to figure out the linear range of Rx, 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!

For starters, what is the voltage at the + input (in terms of Vs)?

EDIT: phyzguy had the same thought.
 
I solved it, I had to solve for a non-inverting (positive) input voltage (vp) first and then created a "new" circuit. Using that circuit I found the output voltage using that equation I listed above while replacing vs with vp . I got vp = [(80k/(80k+20k)]*750 mV = 600 mV

then vo = [(3.3k+46.2k)/3.3k]*600 mV = 9000 mVIt feels good to figure my own answer out...lolEDIT: I didnt refresh, so I didn't see your guys replies. Thanks all! :)
 

Similar threads

  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
15
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 21 ·
Replies
21
Views
4K
  • · Replies 18 ·
Replies
18
Views
3K
Replies
1
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 5 ·
Replies
5
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K