I have a simple non inverting op amp circuit.

Op Amp Circuit

I am using this to amplify a DC voltage. The positive input voltage will vary from 0V-5V.

My problem is that regardless of the input the output is about 22V.

The exact op amp I'm using is here.
Datasheet here

It seems to me that regardless of the input voltage that the output is the saturated max voltage based on the specs.

Voltage Swing

I'm 100% positive that the op amp is connected correctly, as I've checked the connections too many times to count. I also rebuilt the circuit on a different part of the bread board to be sure.

Voltage at the negative input = 3.6 V

I also replaced the op amp with a different op amp, datasheet here and got similar results where 0V into the positive input resulted in about 22V output.

  • 1
    \$\begingroup\$ Have you looked at the output with a scope to see if it's oscillating? The OPA541 requires an external current limit setting resistor you don't show. Add your actual circuit showing all decoupling caps and other external components and maybe a picture of your layout. You mention a breadboard which is probably not the best way to prototype with one of these power amps. Also this is not a rail-to-rail I/O device. Look at the common mode input voltage range. \$\endgroup\$
    – John D
    Jan 27, 2021 at 0:13
  • 1
    \$\begingroup\$ I don't know what's wrong with your circuit but be aware you don't need such monster power resistors in that circuit. Even if the opamp is pegged at 24V only 100mW will be dissipated in the resistors (24*24/5820). \$\endgroup\$
    – td127
    Jan 27, 2021 at 0:36
  • \$\begingroup\$ Show us a pic of what you've actually built. \$\endgroup\$
    – brhans
    Jan 27, 2021 at 0:52
  • 1
    \$\begingroup\$ Datasheet here . Page 5 - common mode Vin range is 3v typ 6v worst case less than +/- Vs - you appear to be using it in singkle supply mode so ground is an illegal input voltage. On their cctc ground is mid wat between V+ and V- \$\endgroup\$
    – Russell McMahon
    Jan 27, 2021 at 1:21
  • \$\begingroup\$ Tip: the earth/ground symbol represents metal plates buried in the ground. They should only point downwards to ground - not into the sky as shown in your schematic. \$\endgroup\$
    – Transistor
    Jan 27, 2021 at 10:38

1 Answer 1


Page 5 of the datasheet shows that this is NOT a single supply amplifier and that Vin may not approach closer than 3V typical or 6V worst case to ground or V+

Your Vin = ground is violating this common mode specification

Your alternative op-amp has the same issue.
The OPA544 opamp - datasheet here - see datasheet page 2 - has a common mode range +/- 4V typical and +/- 6V worst case inside the supply rails. Vin should ideally be at least 6V above your current system ground.

enter image description here

  • \$\begingroup\$ I realize that it is not a single supply amplifier. I did some research, and found that it should work, but I will attempt to connect a negative voltage to it to see if that will work. \$\endgroup\$
    – Smashley
    Jan 27, 2021 at 21:21
  • \$\begingroup\$ @Smashley I do not know what you mean by " ... research ... should work" BUT unless the research rewrites the data sheet specs above then it will not work. If you consider this is not the case you should say what the research found - otherwise you are wasting your time and ours. \$\endgroup\$
    – Russell McMahon
    Jan 28, 2021 at 0:45

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