The output of Op-Amp[LM324] has error as non-inverting Amp

Click For Summary

Discussion Overview

The discussion revolves around the performance of the LM324 operational amplifier in a non-inverting amplifier configuration. Participants explore issues related to gain stability, circuit layout, and power supply requirements, with a focus on both theoretical and practical aspects of using the LM324.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant reports inconsistent gain values when applying different input voltages, questioning whether input offset voltage is the cause of instability.
  • Another participant suggests that a split supply may be necessary for proper operation, especially for AC signals.
  • It is noted that the LM324 can function with a single supply as long as all voltages remain positive, but layout issues may affect performance.
  • Concerns are raised about the potential impact of power supply current sharing with signal wires, which could introduce errors.
  • One participant corrects the gain calculation method, emphasizing that the correct gain for a non-inverting op-amp should include a specific formula.
  • A later reply acknowledges the correction regarding gain calculation and expresses gratitude for the clarification.
  • Another participant shares a successful configuration using different resistor values, resulting in an acceptable output.
  • One participant recommends using MultiSim for troubleshooting circuit issues.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of a split supply and the correct method for calculating gain. There is no consensus on the cause of the gain instability, and multiple perspectives on circuit layout and design considerations are presented.

Contextual Notes

Participants mention potential issues with input voltages being too close to the supply rail and the importance of bypassing the power supply with capacitors. The discussion includes unresolved questions about the specific effects of layout and wiring on circuit performance.

Who May Find This Useful

This discussion may be useful for electronics enthusiasts, students learning about operational amplifiers, and practitioners troubleshooting similar circuit configurations.

booboo1
Messages
2
Reaction score
0
Hi everybody
I'm a newbie and working on LM324 to learn Op-Amp. this is my circuit:

http://img4.uplood.fr/free/qx3o_20150425_172843.jpg
One of the resistors is 217ohm and another 978ohm. then the gain should be 4.50691 as you can see. so far so good. I know this is for ideal Op-Amp. I applied 0.15v to the input and got 0.94v in the output. then the gain is 6.26667. again I applied 0.35v to the input and got 2.03v then gain should be 5.8!?o_O
again I applied 1.86v and got 10.31 then the gain is 5.54301! holy crap! :wideeyed: why isn't the gain stable? because of input offset voltage? How can I stabilize it?
 
Last edited by a moderator:
Engineering news on Phys.org
You need a split supply to make this work.
 
  • Like
Likes   Reactions: booboo1
LM324 should be okay with single supply so long as everything stays positive,.
But if you're inputting AC then yes, you need dual supply.

Did you bypass your supply with a small cap near the IC?

What is voltage at junction of 217 - 978 resistors?
Is it the same as your input?
If opamp is making its inputs equal , the problem is not offset.

Possibly it's your layout. When power supply current shares a wire with signal, the drop along the wire adds to signal.
Is there any AC in your output?
How are your input source and 217 tied to common ?
 
The gain for a non-inverting op-amp is not how you are computing it. The gain in this case is 5.50691. (978/217) + 1. Keep your input voltages farther away from the supply rail with a 324.
 
  • Like
Likes   Reactions: jim hardy
Averagesupernova said:
The gain for a non-inverting op-amp is not how you are computing it.

Thanks - i missed that !
Big ten-duh on me, good buddy !
 
Thanks guys
I used 145.6kohm as Rf and 2.14kohm as Rin and got an acceptable output. for example 70.1mv in the input, I got 4.93v in the output.
 
MultiSim is my best friend when troubleshooting circuits like this. Just a suggestion.
 

Similar threads

What's wrong in my LTspice simulation of an Op-Amp integrator circuit?
  • · Replies 9 ·
Replies
9
Views
7K
How does an opamp work as non-inverting amplifier
  • · Replies 11 ·
Replies
11
Views
3K
How to clasify if it's an inverting/non-inverting op amp
  • · Replies 33 ·
2
Replies
33
Views
6K
How Do Op Amps Respond to Inverting and Non-Inverting Inputs?
  • · Replies 12 ·
Replies
12
Views
3K
How does an Op-Amp "find" equilibrium (w/ Negative Feedback)?
  • · Replies 50 ·
2
Replies
50
Views
8K
Asking for Op Amp recommendations
  • · Replies 7 ·
Replies
7
Views
2K
Any advice to make this Op-Amp temperature controller circuit work?
  • · Replies 34 ·
2
Replies
34
Views
4K
Why is my op-amp frequency response not ideal?
  • · Replies 9 ·
Replies
9
Views
3K
"Class-B" Audio Power Amp with "Current Pumping"
  • · Replies 26 ·
Replies
26
Views
3K
Engineering Analyzing the output impedance and open loop gain of a IC-741 Op-Amp
  • · Replies 2 ·
Replies
2
Views
3K