I have a model resonance circuit that is excited with an auxiliary winding and I need to build an amplifier to be able to amplify the current from the function generator in order to drive the auxiliary winding. I have used an OPA548 in Multisim in order to amplify the generators signal by a factor of 3 and it is current limited to an amp. However when simulating I am getting unexpected outputs across the auxiliary winding (7mH inductor) and I do not know how to resolve this or if this is just a multisim error. Amplifier circuit and output

Here is the resonance circuit. White Circuit

Any help would be appreciated, I've never had to make an amplifier for an inductive load before so i'm not sure what I have to account for.


1 Answer 1


You've made an error here: -

enter image description here

The inverting input should go to the junction of R2 and R3.

Also, driving an inductor directly is somewhat frowned upon given that the likely offset DC voltage from the OPAMP is going to be in the realm of 20 mV and this might be trying to force several amps of DC through the 7 mH inductor.

  • \$\begingroup\$ Thank you, can't believe I missed that! Okay, is there any other way of driving the inductor your can recommend? Would using a transistor amplifier after the op-amp help? Cheers \$\endgroup\$
    – Loue
    Commented Sep 12, 2019 at 10:50
  • \$\begingroup\$ Use a capacitor in series with the inductor to remove any dc offset. \$\endgroup\$
    – Andy aka
    Commented Sep 12, 2019 at 11:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.