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Old 1st March 2010, 01:50 AM   #1
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Default How to identify a quasi-complementary amplifier?

How to identify a quasi-complementary amplifier? is it it contains 4 transistors 2 in 1 pair. And each pair is in complement? Does anyone can share some info about quasi-complementary amplifier?

thank you.
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Old 1st March 2010, 02:08 AM   #2
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All output devices are the same type and number.

Either all npn, or all pnp.
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Old 1st March 2010, 02:15 AM   #3
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I believe its common to find all NPN as outputs due to PNP's being difficult to make in the early to mid 70s.
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Old 1st March 2010, 10:06 AM   #4
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Default How to identify a quasi-complementary amplifier?

This is a good question.

Quote:
Originally Posted by AKSA View Post
All output devices are the same type and number.
Either all npn, or all pnp.
Really? Then I must even call the CSPP (Circlotron) and the topologies from Ollson (Better Audio from non complements? from Bengt Olsson, Electronics World + Wireless World, December 1994 page 988) quasi complementary?

I don't think so. I call only such output stages as "Quasi complementary", if it looks like PP true complementary buffer except the lower last power transistor. This means for me, that the upper halve of PP buffer looks like a darlington and the lower looks like a sziklai (CFP) darlington

An complete overview of topologies, where are only NPN-BjT's and N-CH MOSFET's in the last part of power buffer you will find here:
Only N-Channel MOSFETs (NMOS); better Audio from non complements by Audio Power?

also of interest in this case are some articles from the diyaudio member "X-PRO", e. g.
Quasi or not Quasi - that is the question

Last edited by tiefbassuebertr; 1st March 2010 at 10:10 AM.
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Old 1st March 2010, 12:11 PM   #5
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Quote:
Originally Posted by motbuddy View Post
How to identify a quasi-complementary amplifier? is it it contains 4 transistors 2 in 1 pair. And each pair is in complement? Does anyone can share some info about quasi-complementary amplifier?

thank you.
Quasi means acts as if.
So quasi complimentary means the NPN's act as if they were complimentary.

In reality that isnt quite true as one side has more gain than the other due to one side requiring an inverting driver which has gain, where as the other side is a simple driver buffer.

I found the inverting side required a capacitor from collector to base on teh driver transistor to stop oscilation.
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Old 1st March 2010, 01:07 PM   #6
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Quote:
Originally Posted by nigelwright7557 View Post
In reality that isnt quite true as one side has more gain than the other due to one side requiring an inverting driver which has gain, where as the other side is a simple driver buffer.
Yes, and therefore some manufacturers like Quad (model 303, not to interch. to the current dumping version 405) creates three stage super devices to avoid (or reduce at least) this disadvantage (see attachement).
But the disadvantage there is the risc of oscillation of the buffer stages itself (not so by use of two stage, darlington for upper and sziklai darlington for lower buffer part.
Only truly experienced (and unfortunately very few) developers (like Quad) achieve a design without any oscillation under any load condition. By many others there are oscillation and hum/buzzing effects through the sensitivity of parasitic influences. If I get such amp devices I must remove one stage in any cases, i. e. the reduce to a two stage PP buffer

By the way, after right service and maintenance the Quad 303 is a very fine sounded amplifier, (much more better than the current dumping version Quad 405 and most true complementary versions). Only power stage versions with much more idle current trough the output can outperform the Quad 303

http://www.net-audio.co.uk/quad303upgrade.html
Quad 33 and Quad 303
Quad 303 : Upgrade output stage to be fully complementary
Quad 303 triple cascade
Attached Images
File Type: jpg quad303 power PP super buffer.jpg (28.9 KB, 738 views)
File Type: jpg quad303m.jpg (98.3 KB, 724 views)
File Type: jpg Quad 303 inside.jpg (212.9 KB, 710 views)

Last edited by tiefbassuebertr; 1st March 2010 at 01:27 PM.
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Old 1st March 2010, 02:05 PM   #7
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here basic articles:
Attached Files
File Type: zip Bax.zip (66.3 KB, 138 views)
File Type: zip Lin.zip (63.3 KB, 82 views)
File Type: zip QuadTriple.zip (28.5 KB, 93 views)
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Old 4th March 2010, 03:22 AM   #8
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Does this claim about quasi-complementary correct?

Quote:
Designers also sometimes use a "quasi-complementary" configuration, which uses a Darlington push pair (i.e., two NPN transistors) and a Sziklai pull pair (i.e., one PNP and one NPN transistor). This configuration, which uses three NPN transistors and one PNP transistor, is advantageous because:
  • Silicon PNP transistors have historically been more expensive than their NPN counterparts.[citation needed]
  • The performance of the lower pull pair, which uses a single NPN transistor, more closely matches the performance of the upper push pair, which consists of two NPN transistors.[citation needed]
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Old 24th April 2011, 11:59 AM   #9
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Quote:
Originally Posted by motbuddy View Post
Does this claim about quasi-complementary correct?
Who can perform an exactly investigation of both?
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