Method of compensation of the gains - diyAudio
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Old 12th January 2013, 05:55 PM   #1
Stee is offline Stee  Italy
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Default Method of compensation of the gains

To obtain a perfectly complementary amplifier is appropriate to use components homogeneous both in the stadium in voltage at the stage at which current
to address the disparities that exist between the selected components N and P can use this configuration:

GN * GP = GRail+
GP * GN = GRail-
Grail+ = GRail-
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Old 12th January 2013, 06:16 PM   #2
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So, you are saying that to have an optimum performing amplifier, all the complementary transistors should have matched Hfe
at the quiescent conditions (idling bias). Is that what you mean?

If so, it will be a very difficult and expensive requirement, should you decide to change the bias after installing all the carefully matched parts.
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Old 12th January 2013, 10:05 PM   #3
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How about negative feedback? Isnt it was designed to get rid of components non-linearity? =)
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Old 13th January 2013, 12:14 PM   #4
Stee is offline Stee  Italy
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Default Don't worry about bias

need just ADD a NPN (BC546) + trimmer 22K across diodes
see new diagram for perfect gain compensation

about feedback need just a little part of partition
http://www.esafono.it/Esoter%20Evoqu...0Amplifier.pdf

shortly publish overview of the completed
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Last edited by Stee; 13th January 2013 at 12:26 PM.
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Old 13th January 2013, 01:45 PM   #5
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'Still don't follow what you are saying about device Hfe matching and why it must be done even for quite different circuit functions.
eg: The LTP and VAS transistors as shown in your first post.
This certainly conflicts with current design practice on this forum, at least.

Can you be clearer specifying what it is you are trying to tell us? I can see that you are saying the Hfe should be balanced for mirror halves,
that is a well known refinement, I believe.
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Last edited by Ian Finch; 13th January 2013 at 01:48 PM.
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Old 13th January 2013, 04:48 PM   #6
Stee is offline Stee  Italy
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Default GAIN GAP

explain how it gets boring involves the selection of a feature on the population and how it distributes between two complementary families


the name of this AMP is EXCELSUS
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File Type: pdf EXCELSUS.pdf (204.0 KB, 12 views)
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Old 13th January 2013, 04:56 PM   #7
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Quote:
Originally Posted by Stee View Post
To obtain a perfectly complementary amplifier is appropriate to use components homogeneous both in the stadium in voltage at the stage at which current
to address the disparities that exist between the selected components N and P can use this configuration:

GN * GP = GRail+
GP * GN = GRail-
Grail+ = GRail-
Stee, what you show here is a quasi-complimentary output stage.
If you Google on that, you will find some additional refinements. Matching the Hfe is only limited effective, because the drivers see very different load impedances from the output devices during a signal cycle.
People like Peter Walker and I believe John Linsley Hood have studied this and came up with very good refinements.

jan
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Old 13th January 2013, 05:10 PM   #8
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Hi,

Anyone who thinks hfe can be defined to 3 significant digits
is barking up the wrong tree, same with the total hfe's
having much to do with the amplifiers gain structure.

Fabulous "pointless" features of an amplifier are just
window-dressing, bypassing thorough understanding.

rgds, sreten.
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Old 14th January 2013, 05:04 AM   #9
Stee is offline Stee  Italy
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Default thanks @ all

see last version of EXCELSUS AMP
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Old 14th January 2013, 06:49 AM   #10
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I don't believe this design outlined in the PDF addresses the issues you raised in post 1. The block diagram appears symmetrical on paper but that is about all - there is no evidence beyond concept that it has any benefit to resolving transistor complementary differences, electrically or even sonically speaking.

If you want to design worthwhile circuits, you need to understand solid-state electronics a little better to grasp how electrical and diagrammatic balance differs and what are realistic expectations for semiconductor "matching".

The bigger question is why you believe duplicating an amplifier circuit and then matching each carefully so as to rejoin them in parallel with transformers achieves anything tangible. Does it?
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