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Old 17th May 2005, 01:41 PM   #1
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Smile Best Input differential configuration in amplifiers.

Hi everyone,

Just fascinated by the various topologies used at input stages of an amplifier, such as,
1 Single Ended Differential
2 Dual Differential
3 Diamond Differential
4 Cascode loaded Differential [dual and single ofcourse]
5 Cascaded Differential


What is the best configuration for an amplifier input stage according to your experience.

So , guys lets start another thread dedicated to our differential stage topologies.



cheers,
Kanwar
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Old 17th May 2005, 02:26 PM   #2
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Hi, Kanwar,

I think you missed putting 5 pictures

Semantics could be a big problem here.
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Old 17th May 2005, 02:50 PM   #3
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The diamond differential............
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Old 17th May 2005, 02:51 PM   #4
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The dual differential...........
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Old 17th May 2005, 02:55 PM   #5
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Cascaded differential............
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Old 17th May 2005, 02:58 PM   #6
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cascode loaded differential.............
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Old 17th May 2005, 03:07 PM   #7
zinsula is offline zinsula  Switzerland
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Replace the bjt's with J-Fets in your diamond differential, get rid of the biasing diodes, and so you have my favourite.

You might cascode those to use higher than 15-20V rails though.

Cheers, Tino

BTW, something similar to your diamond differential is used in LM6172 and LT1364, afaik.
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Old 17th May 2005, 03:56 PM   #8
00940 is offline 00940  Belgium
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What about the topology at the lower right ?

Click the image to open in full size.


From : http://peufeu.free.fr/audio/memory/m...-circuits.html
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Old 17th May 2005, 04:52 PM   #9
sam9 is offline sam9  United States
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Just my opinion: A-Standard Configuration is "good enough" up to 150W-200W. By this I mean that the improvements afforded by other configurations are incrementally small and likely disappear under XO-distortion and the noise floor.

However, higher power amplifiers generally mean higher CL gain which could be enough to make the improvements more easily audible. It has been remarked on, and I've leard it myself, that some very high power amps have enough gain to make even thermal (Johnson) noise audible when idle.

Going back to the standard configuration -- For self constructed amplifiers, fewer components means fewer oportunitities to screw up, fewer component to fail, fewer potential bad solder joints, fewer things to investigate when the &%$$^&*=% doesn't work, fewer component pairs needeing matching. It means a smaller PCB footprint which makes it easier to do a good enclusure layout and wiring scheme. If the topology is single sided rather than mirror image, a current mirror can be added which may well provide benefits virtually equal to the more complex circuits.

If I had the time I would probably try building all the other configurations just because they look cool. I must remind myself that I should allocate some (MORE) of my time to listening to what I build rather than let it all be totally absorbed by the next great idea.
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Old 17th May 2005, 06:21 PM   #10
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Default Re: Best Input differential configuration in amplifiers.

Quote:
Originally posted by Workhorse
What is the best configuration for an amplifier input stage according to your experience.
For me it's been number 6, the transformer differential.

Click the image to open in full size.

se
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