Class Ab Oposite Topology

i come across this schematic which looks very nice but can somebody tell me this reverse topology like having the matching resistors in the power supply section exactly oposite than normal design ....does it beneffit something ????

design wise or electrically looking at actually its the same thing but when you design amps there should be a difference ..... any opinions ????


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It is a Sziklay (spelling ??) output stage. It can be designed with voltage-gain >1. And this has actually been done here. One of the practical advantages is the possible usage of driver transistors with lower Vce capability in this case.
A practical disadvantage are possible stability problems (C8 and C9 are there for a reason !!).

A theroretical advantage is to create a nested NFB loop with high loop gain. How much practicla advantage can be taken from this depends on the designer's skills.




2007-09-28 10:21 am
Hi guys,

Sakis, search for ETI-480. That's an Aussie 50/100W amplifier design from the late 70's.
Strange translation, Sakis (bad translation software maybe?). I cannot see any "matching" resistors in any power supply here. You attached the schematic of the ETI-480 amplifier - I cannot see any power supply circuit. Maybe you mentioned "output stage"?
The same about "reverse topology". I can't see any reverse topology here.

PhaseAccurate, you're almost right about spelling. He was called "Sziklai". He born (or he was living there?) in Mid-Europe, Hungary.
i presume

you like to have a detailed explanation

there you go......

matching resistors are the resistors located normaly in the emmiter of every output transistor in cases of more than two transistor exist to match the digfference between the two transistor .....

normally this setup is located in the output section IE the collector of the transistor is tied to the power supply and the emmiter to the output of the amp .....

this one is the oposite ......

beyond the defination of terms i was looking for some information about the one or the other topology and why .....and this also refers to the output stage not the drive circuit ......