Need Help on Calculations for Negative TL431 with Pass Transistors!!

[hermanv]

I've had trouble with the stability of the TL431. The ON Semi data sheet warns about minimum current and pretty much assumes a large capacitor anode to cathode. I had some luck with a smaller capacitor cathode to feedback pin but be careful. There is a negative resistance state as the power is first applied, some circuits hang and won't pass this point without the large byass cap. It took a lot of work to find an unconditionally stable solution.

No it wasn't this amp it was in an isolated power supply feedback loop. So my difficulty or results may not apply.