Saving an LM324 Amplifier with YUNGMAN's Trick

[Ravaner]

Hello. This post is mainly dedicated to YUNGMAN. I used your trick with Transorb in a class B amplifier driving coils. Unfortunataly these Transorbs introduced more than 1 nF capacitance and so the amplifier produce a large high frequency oscillation. Without Transorb, one more time LM324 is burned. Do you have an other idea ? Thanks by advance.

 

[berkeman]

Hello. This post is mainly dedicated to YUNGMAN. I used your trick with Transorb in a class B amplifier driving coils. Unfortunataly these Transorbs introduced more than 1 nF capacitance and so the amplifier produce a large high frequency oscillation. Without Transorb, one more time LM324 is burned. Do you have an other idea ? Thanks by advance.

To drive a capacitive load, the usual trick is to drive it through a series resistor. How big of a series resistor can you use in your application? Or did you solve this problem another way?

 

[yungman]

Hello. This post is mainly dedicated to YUNGMAN. I used your trick with Transorb in a class B amplifier driving coils. Unfortunataly these Transorbs introduced more than 1 nF capacitance and so the amplifier produce a large high frequency oscillation. Without Transorb, one more time LM324 is burned. Do you have an other idea ? Thanks by advance.

My god, I post dedicated for me!

Anyway, they have smaller and lower capacitance transorbs. Go to Digikey:

http://www.digikey.com/scripts/dksearch/dksus.dll

Type TVS array,

This is one of the example:

http://www.infineon.com/dgdl/esd5v3u4rrs.pdf?folderId=db3a30431441fb5d011488a9e66f0ded&fileId=db3a30431c69a49d011cad6ae0c10a10There are plenty bus TVS array that you can look into. I don't remember what I said in the last post anymore for very obvious reason...OLD AGE! Like Berkeman advice, if you worry about those small TVS can't handle the power, put a small series resistance from the board input to the op-amp input. Then put the TVS right at the input. You'll be surprised even a few hundred ohms can really protect the op-amp.