Balanced IGBT for amplifier output

[Lazy Cat]

Here is my version of IGBT named B-IGBT, like balanced IGBT, very suitable for the output stage of an amplifier.

Very easy to drive, input MOS-FET drives the same current for both output transistors etc.

Output NPN/PNP's can be paralleled to raise current capability.

Brainstorming: please post suggestions for complete high performance amplifier including this output B-IGBT.

[Lazy Cat]

Maybe something like this would be a good starting proposal.

[jan.didden]

Ingenius circuit! Haven't seen that. Possible drawback: the output cannot swing close to the rail as there is no possibility to feed the mosfet with a higher supply voltage, and there are two Re's in series which also limits output level with high currents. You'll need a higher supply voltage than usual for a specific output.
Other than that, why not try it. You probably can tack it onto a 'normal' Vas driver.

Jan Didden

[Lazy Cat]

Well Jan, first thanks, than some explanations.

Output rails are +/- 50V and are separate from supply rails of voltage amplifier; these can be arbitrary from +/- 55V up.

Two resistors valued 22ohms flows driver current and therefore are not influential to output current nor limits it.

I have to remind you that MOS-FET's are drivers here.

[megajocke]

A potential problem I see - the NPN:s and PNP:s might not share current that well under all conditions. This is because they are driven with about the same current but current gains can be all over the place. Maybe beta-droop comes to your rescue though.

Doesn't Bryston use something similar but with BJT drivers?

[lineup]

technically it is like parallel 2 output transistors, but using one PNP+ one NPN

what you pay is some extra volt drop
what you gain is: ????

[Workhorse]

Replace the mosfet driver with bipolar and you will have Quad complementary output stage of Bryston amps..........nothing new

[Lazy Cat]

What we are talking about here is new version of Insulated Gate Bipolar Transistor or IGBT semiconductor in balanced configuration (BIGBT).

Implementations of BIGBT device are versatile and can be used in output stages of different kind of power devices.

Current devided among NPN/PNP devices is similar like in parallel configuration, the transistors have to have similar-equal Hfe. MOS-FET driver is symmetricaly loaded with one BE current per output pair.

In audio:
What you gain is voltage driven powerful output device which can be easily managed by VAS stage. That means you need less stages and shorter signal path is guaranteed. Also you gain positive performance of both kind of output configuration: common emitter and common collector follower.

[megajocke]

BJTs are voltage driven too Drive current doesn't fall with decreasing frequency though like with mosfets.

[Lazy Cat]

Megajocke I know that you're very curious about post#2 so why don't you just try it.

It's my favourite output stage by far and believe me I tried them all.