Search for the better MosfetPowerFollower..

[bogdan_borko]

HI!

This topology is what we all talked about a number of times but IMO there is still not good enough.

I experimented a long time in the search of the "ideal" mosfet power follower...
This is what I came up to.

INput inpedance is about 12K.Distortion figures are lot better then the classic PP type follower. Q1 and Q2 work like a constant voltage sources, floating with the input voltage, giving constant bias voltage for output mosfets.
The following ciruit is biased in class A (2.2A idle current)(30W class A) but it could be easily biased to work in class AB but then Q1 and Q2 are used for thermal tracking (this is not tried in practice).
Input stage is biased with 2.2mA.

What do you think? Are there any solutions to make this desing better and to raise input impedance so it could be driven directli from the tube stage.

Cheers!

 

[AndrewT]

Hi,
you made a comparison to a classic PP stage.
Does your's operate in PP?

12k fed from a tube follower might be OK.
Without a follower, output impedance might be a bit too high.

 

[bogdan_borko]

Does your's operate in PP?

what do you mean??

nobody interested?

 

[AndrewT]

Hi,
you used the term here

better then the classic PP type follower

I thought you knew what you were talking about.

I understood it to mean Push Pull.

 

[bogdan_borko]

the circuit I posted is a push pull(PP) folower and it has better distortion figures then a classic type pp follower seen in the hybrid amps round here, that`s wath I meant...

 

[bogdan_borko]

so, I`m gonna quote my sefl :

What do you think? Are there any solutions to make this desing better

 

[bogdan_borko]

so, I`m gonna quote my sefl :

What do you think? Are there any solutions to make this desing better

anyone tried something like this?

 

[LBHajdu]

That’s a really nice amp. What does it should like? What are the distortion figures on it exactly?

This topology would really be appreciated more in the pass labs forum.

Leve

 

[powerbecker]

Bogdan:
"anyone tried something like this?"

Hello Bogdan,
no!
I believe that the input impedance from your follower can be fairly low at higher frequencies.
Also your arrangement looks like to need carefully adjustments for optimum results.
Can You give some specs?
Can be interesting what you get when You drive it from a 5k source!

For a answer to your question please look at the attachment.
It´s from (C) Mario Benndorf, Essen am 24.07.2006
I see it here:
http://www.moehrenbude.de
Regards
Heinz!