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PostPosted: February 13th, 2017, 2:26 am 
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Joined: February 13th, 2017, 1:51 am
Posts: 2
Hi everybody,

I am trying to build a high power/current function generator. And I’m using a program called TTG as a function generator using my PC sound card, then I am trying to amplify the signal.

I am using an LM324N, I was successful to amplify the voltage from ~0.01V (my sound card output) to about 1.1VAC (testing sine wave for now), however when I measure short circuit current of the output it’s a mere 40ma.

Am i doing something wrong here? Or do op-amps really give little current? And how should I go about amplifying the signal enough so it can drive... let's say a little ac motor.

FYI, here's some details of LM324N:

Thanks in advance!

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PostPosted: February 13th, 2017, 7:33 pm 
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Joined: December 6th, 2004, 9:00 am
Posts: 7611
Location: Aachen (Germany)
That's by design. OpAmps are made to amplify the signal (voltage), not the not the power (current).
It's flat out impossible to draw enough power from the Soundcard to drive a motor.
Have you never wondered why PC speakers come with their own PSU and don't draw the power from the Soundcard?
Or why you can't connect pasive speakers directly to the soundcard and need an audio amplifier or stereo in between? (Hint: It's not because passive speakers are lacking a 3.5mm plug)

Just add a power supply to your motor and draw the current from there. You can still apply the signal line from the computer.

Benedikt Bauer - SVS (Spacial Volunteer Support)

We're offering custom PAL / PHP code and general SAM assistance at

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