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Stee 21st January 2013 12:47 PM

Twin Output Stage
2 Attachment(s)
With unity gain of the CFP
it is easy to double cells without problems :sax:

Osvaldo de Banfield 21st January 2013 02:47 PM

Mmm, believe gain<1. They are only emitter followers, and resistor current share. A classical stage.

Stee 21st January 2013 06:14 PM

What about VAS?

Osvaldo de Banfield 21st January 2013 06:20 PM


Originally Posted by Stee (

Nothing new: an operational amplifier made with discrete material. I believe that there are some elements idle in the power stage, with only one driver, you can handle base current for 2 or 3 final transistors, saving the cost and space in board.

Stee 22nd January 2013 05:48 AM

They are not only emitter followers - check for Complementary Feedback Pair here

Copyright infringing URL removed

east electronics 22nd January 2013 12:21 PM

nothing new its done before in the Alchemist forcetti

Double sziklai pairs can be pain in the a** to stabilize and often require huge miller caps to achieve a safety ( marginal )

Osvaldo de Banfield 22nd January 2013 01:02 PM


wahab 22nd January 2013 02:16 PM

The schematic on the left look like it was extracted from Bob Cordell s book...

Stee 22nd January 2013 04:38 PM

stabilize CFP
1 Attachment(s)
Probably the CFP should be tripled or quadrupled

this allows to increase the resistance of pull-up and directly the stability of the single cell

the output resistance of the cell involves a self-adjustment
greater is its slope in the graph of the drift
the greater its effectiveness

east electronics 22nd January 2013 04:54 PM


you are wrong might work in simulation but in real life will have thermal stability issues ,gain from stage to stage issues,will be by far pcb depending and eventually run to oscillation ..Adding miller caps to keep it stable will kill all the sonics

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