Hi,

I am currently using the LM3886 in a parallel setup as explained in app note. AN-1192.

I am using it to drive the DC supply of a Radio - which draws approx 6A at 12V, so essentially a 2ohm load.

I was previously using the LM4766 in a bridged setup, but this was for a radio drawing 1A at 12V - which worked perfectly.

Due to the increased power I looked at using the LM3886 in parallel as this looked like it could provide enough power easily.

When testing on a test load, set at 100 ohms, the parallel setup worked fine. As soon as I dropped the resistance to 12Ohms, the output of the amplifier became unstable. I think this is due to the IC's getting too hot?
The IC's are heatsinked and have a fan on them - so this shouldnt be the case? Maybe this is due to some sort of inbalance between the 2 IC's? They are both set with a gain of 2 - 0.1% resistors, and have an output series resistor with a value of 0.1Ohms. Power supply is +/-24V.

When driven individually, they work fine, its only when in a parallel setup I am seeing the problems.

Any ideas on what is going wrong?

Thanks

 

Circuit schematic ?

Ramesh

 

As Rasmussons said, we need a schematic.
LM3886 is intended to be used as an audio amplifier. Why are you trying to use it as a power supply regulator?

 

Hi,

I am currently using the LM3886 in a parallel setup as explained in app note. AN-1192.

I am using it to drive the DC supply of a Radio - which draws approx 6A at 12V, so essentially a 2ohm load.

I was previously using the LM4766 in a bridged setup, but this was for a radio drawing 1A at 12V - which worked perfectly.

Due to the increased power I looked at using the LM3886 in parallel as this looked like it could provide enough power easily.

When testing on a test load, set at 100 ohms, the parallel setup worked fine. As soon as I dropped the resistance to 12Ohms, the output of the amplifier became unstable. I think this is due to the IC's getting too hot?
The IC's are heatsinked and have a fan on them - so this shouldnt be the case? Maybe this is due to some sort of inbalance between the 2 IC's? They are both set with a gain of 2 - 0.1% resistors, and have an output series resistor with a value of 0.1Ohms. Power supply is +/-24V.

When driven individually, they work fine, its only when in a parallel setup I am seeing the problems.

Any ideas on what is going wrong?

Thanks

Makes no sense to try to use a audio amp as a DC voltage regulator.

You could easily build a 6A linear reg with the LP2975:

http://www.ti.com/product/lp2975

 

They are both set with a gain of 2

The LM3886 is designed to be stable at closed-loop gains of 10 or greater.

 

Has Alice gone back to Wonderland?