GC with LM3875 as a voltage regulator also

[GregGC]

Reading some of the treads I find people like and use those power amps as voltage regulators. Has anyone experimented with the following setup:

- NIGC/IGC using LM3875/OPA541
- Regulated PS using the same LM3875/OPA541 with lots of capacitance in front of the voltage regulator (like in Pedja's reg sch.)
It would be interesting to see what happens. May be a totally new animal.

Hey Pedja, maybe you can shed some light here.

Thanks

Greg

[theChris]

my bet would be the protection circuity in the lm3875 would prevent it from being an effective regulator.

[GregGC]

Didn't think of it. OPA541 with no CL resistor then.

[theChris]

without the current limit resistor i think it still will limit current, just at a different value. pretty sure it lists curves or values for such in the datasheet.

[tbla]

why don't you try the lm338 regulator - just like pedja - you might like it......or the lt1083.

[GregGC]

This was just a thought. I will try it one day. I have to finish the Classic version first (unregulated, 1000uF/rail).

[Pedja]

Originally posted by GregGC
Hey Pedja, maybe you can shed some light here.

Hello Greg,

Actually I don’t feel so, but as I am named… I have some thoughts.

If you settle on the feedbacked regulator it is easier and safer to use the LM338 (or more expensive 1083/1084) which is the device designed for such purpose. Anyway, the usage of the LM3875 and similar not unity gain stable chips is not good idea since the voltage reference (and its noise) must be amplified (10 times minimum). The OPA541 (or something similar) looks more appropriate but probably can’t drive capacitive load directly. Some series resistive decoupling at the output still might be a way to go (BB offers spice models and some short sims I ran earlier for the OPA549 seemed promising). Using unity gain chip and low noise voltage reference you can probably achieve better noise figure than with the integrated regulators but neither I am sure that will bring much of anything nor I could see some other advantage.

Pedja

[GregGC]

Thanks!
Makes sense.