I have built a sine wave oscillator circuit that outputs 3V@1Khz peak to peak, I am trying to connect the circuit output to a transformer(TRIAD-vpl2-4000) in order to amplify the voltage, I connected a buffer(OP07C8 manufactured by ST) between the circuit output to the transformer input in order to push more current to the transformer.circuit output below circuit output

When I connect the transformer to wave generator with output impedance of 50[Ohm] I get a clean sine wave on the transformer output, but when I connect the transformer to the circuit the output gets distorted, can anyone please explain what is the reason for that ?enter image description here

I measured about ~65mA(pk2pk) at the transformer input when is connected to the circuit and 50mA(pk2pk) when connected to the wave generator (assuming the voltage output from the circuit and generator is the same, 3V) So, I don’t think it is an issue of input current to transformer since generator and circuit provide similar currents.

Is this setup can even work ? or should I start look for a different transformer? Any help would be much appreciated


EDIT: Updated out waveform when not connected to a transformer: Updated waveform from output

  • 1
    \$\begingroup\$ can you post a picture of your buffer's output without the transformer? your pictures pretty much look like you're driving the transformer with a square wave. \$\endgroup\$ May 19, 2017 at 8:50
  • \$\begingroup\$ hi marcus here is the buffer output when is not connected to the transformer pasteboard.co/51f29xnr.jpg \$\endgroup\$
    – I.kal
    May 19, 2017 at 9:16
  • \$\begingroup\$ @I.kal Added the image for you. In the future, please use the edit function and crop and reduce the size to something suitable. \$\endgroup\$
    – winny
    May 19, 2017 at 9:22
  • \$\begingroup\$ A transformer does not transform power. Your input does not have enough power to drive your output. You cannot get something for nothing. \$\endgroup\$ May 19, 2017 at 11:05

1 Answer 1


Your transformer's primary inductance is 4.6 mH (according to your circuit). At 1 kHz this has an impedance of about 29 ohms. Normal op-amps won't drive this sort of load. Try adding a transistor push-pull stage or a class A amplifier.

If you read the data sheet you will see that the output is pretty much zero when driving anything approaching 10mA out. The data sheet also indicates that a 1 kohm load is probably about where you should be heading.

So you can either make your inductance a lot higher or make your operating frequency a lot higher or add a buffer than can supply the current needed to magnetize the core.


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.