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Old 22nd January 2013, 05:02 PM   #11
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Again, this stage has been working some decades, discrete or inside a chip. I don't know what Stee want to invent. As I said, it is a classic stage of a pair of transistors emulating a darlington as emitter follower, gain less than one in voltage, several times in current.
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Old 22nd January 2013, 05:25 PM   #12
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@osvalldo

Please point out some schematics that you have seen a similar circuit working
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Old 22nd January 2013, 05:38 PM   #13
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Here. STK4131V and much more.
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Old 22nd January 2013, 05:55 PM   #14
SY is offline SY  United States
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Quote:
Originally Posted by Stee View Post
They are not only emitter followers - check for Complementary Feedback Pair here
Blatant copyright infringement (in this case Bob Cordell's book) is illegal. By hosting this and linking to it, you are literally stealing from Bob. I have sent a note to him to inform his publishers.
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Old 22nd January 2013, 10:23 PM   #15
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Default paralleling CFP

It's hard to put multiple units in parallel CFP
is shown by the fact that they've never seen...
it may be that we miss a piece:
the bias resistor
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Old 23rd January 2013, 03:24 AM   #16
Stee is offline Stee  Italy
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Default DIAMOND CFP

in truth the best way to stabilize the two branches of (single) CFP
is to introduce the diamond input
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Old 23rd January 2013, 06:41 AM   #17
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@ osvaldo

either you are trying to explain something else that is not possible for me to understand .Stee's topology is sziklai the topology you are showing is a all NPN quasi complementary .

@Stee
I will try to keep it as simple is possible ...In an sziklai output scheme the real outputs are the drivers ...voltage come out from them then the big transistors ""open"" according to the demands of the driver ( in this case real outputs ) to provide the current .

That is why you need to monitor temperature at the drivers and not at the output

Then again if you sim a circuit that have badly matched drivers or change hfe or beta according to temperature in order to observe behavior you will understand what i mean.

Farther more in this case matched drivers but most important on a common heatsink separated from the outputs will perform the best and stable from temperature aspects .

In a case that one wants to repeat the sziklai pair that can be very pcb tricky since if gain of stage a to stage b can be different for the above reasons plus tolerance of parts and pcb traces will eventually come to oscillation .

Perfectly made pcb well matched parts i can also imagine one heatsink to accommodate all the drivers and the bias proper distribution of power proper rail decoupling might get you there ... The designers of Alchemist claim that the double sziklai pair (2 drivers+2outputs X2 ) output scheme has amazing ""kick" next to a classic EFP scheme .

To my understanding the input configuration either LTP or diamond will add nothing to the stability of the output schema ...An sziklai pair in the output will ""work on its own"" perform in a way that will not take in account what happens in the input ( the big transistors in the output have no idea what is going on in the rest of the amplifier these are only working as workhorses providing current ) .

( the above on its own is the number one reason why sziklai pairs are notorious for stability issues point is that: if CFP is stable and designed properly can beat the crap of a classic EFP at least in a level of 2 transistors only in the output )

Kind regards
sakis
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Last edited by east electronics; 23rd January 2013 at 06:49 AM.
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Old 23rd January 2013, 07:05 AM   #18
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each and every one of us starting on electronics one of the first things we constructed was a variable power supply ...a bench power supply

some of them was based on partially discrete with 741 and 2N3055 some others based on LM723 and also 2N3055 and some others ( fewer to my understanding) performed the standard Lm317 application with a passive PNP transistor .

Understanding how this circuit works and then you know a few more about sziklai amplifiers understanding how critical is for the LM 317 feedback to work properly then again you know some more about sziklai amps .

For the record from all the above configurations the LM317+PNP is the most tolerant when it comes to load ,shorts, and current ....durable in a few words

kind regards
sakis
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Old 23rd January 2013, 07:12 AM   #19
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once more on the basic application of TDA 2030 there is a schema that works on a single rail supply and a pair of passive transistor .

Actually this amplifier is based on about the same idea and while performance is limited according to the TDA 2030 specs( plus the single rail and the capacitor in the output ) yet again power is limited BUt the specific amp produces quite unique sonics and its extremely tolerant to a variety of loads has very good drive ability in often drive very low load without problems

This as an idea is also to be food for thinking ...when it comes to principal of operation
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Last edited by east electronics; 23rd January 2013 at 07:14 AM.
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Old 23rd January 2013, 11:33 AM   #20
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Quote:
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@ osvaldo
either you are trying to explain something else that is not possible for me to understand .Stee's topology is sziklai the topology you are showing is a all NPN quasi complementary.
I don't know the name of this topology, nor the name who invented it, but it still is a classic one. The NPN output transistor driven by a PNP is like a bigger PNP BJT, and the reversal is also true. I learned it in my secondary school. And I found it in thousands of circuits, discretes or making part of voltage regulator or audio power stages.

Here is another discrete example. Please, view what I rounded!
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Last edited by Osvaldo de Banfield; 23rd January 2013 at 11:46 AM.
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