Plecto
Full Member level 5

Hi. Here's a circuit I've made. The regulator is a negative one (LM337): https://www.circuitlab.com/circuit/srbwgm/class-ab-amp/
I first tried it with a NPN and a positive regulator (LM317), but the amp just kept on oscillating no matter what I did. I added caps from supply to ground, cap in the feedback path, but nothing. I even tried shorting the feedback path completely, but the output still kept on oscillating with a frequency of about 140-150khz. I then tried the design I just linked and got the exact same problem. I now have a short between the output and the non-inverting input, but it's still oscillating at 100-130khz (strange looking wave). Is the design valid and that it's only my breadboard design that causes this?
I first tried it with a NPN and a positive regulator (LM317), but the amp just kept on oscillating no matter what I did. I added caps from supply to ground, cap in the feedback path, but nothing. I even tried shorting the feedback path completely, but the output still kept on oscillating with a frequency of about 140-150khz. I then tried the design I just linked and got the exact same problem. I now have a short between the output and the non-inverting input, but it's still oscillating at 100-130khz (strange looking wave). Is the design valid and that it's only my breadboard design that causes this?
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