Lowdrop, lowsat Power Devices. Sqeezing a 12v supply.

[lineup]

1. Do you know which power devices, TO-220 and larger,
which have very low SAT for power amplifier?
And which power devices has NOT low dropout?

The circuit I desined after a guy asked for amplifier working in single 12V supply.
I use an OPA134 and output stage with voltage gain.
Result is 2.04 Watt into 8 Ohm.
To get twice as much power out we naturally should use 4 Ohm speakers.
The dropout voltage, from 6.0V, is only 0.28V.
This was acheived with MJE15030/31
MJE15030/31 seems to have low sat.

1. It it possible to make a more simple amplifier
that also has rail-to-rail output?

[john_ellis]

Hi lineup
I think you have a good choice for output devices with R-2-R swing. On this occasion (low voltage) there is an argument for complementary-Darlingtons-with-gain.
I have tried complementary Darlingtons with double bootstrap drive but this still has ~0.9V (a Vbe+Vce(sat)) dropout. The only other approach I have looked at is to use a single transistor pair (modern high gain type) with double bootstrap drive which should match your dropout performance but takes quite a bit of driver stage current (double bootstrap VAS).
For just a few watts output some of the new Diodes-Zetex transistors with high gain (~100 min) at 1...2A or so might do nicely. These can dissipate around 1W or so so could be a good match.


John

[lineup]

Doing some bootstrap.
Nice circuit.
Zetex has some intesresting transistors.
I remember I simulated a very low voltage amp using Zetex for lowest Vbe.
It was like 0.45V Vbe.

Actually I got a couple of 0.01V lower when running my circuit
with 2SC5200/2SA1943.
Which show us that 2SC5200/2SA1943 are very lowsat devices.