Has anyone seen this front-end before?

Edmond Stuart · 27th March 2012, 10:22 AM

To all,

Regarding the circuit as shown below, I like to know whether anyone has seen this front-end before. If so, I'm curious to learn more about it and how it behaves in real life. More details can be found here.
(BTW, I'm still editing and updating that page, so it's not yet finished)

Cheers,
E.

Osvaldo de Banfield · 27th March 2012, 12:33 PM

It is a complementary differential amplifier, but is drawing in a some curious way.

Edmond Stuart · 27th March 2012, 12:50 PM

>but is drawing in a some curious way
Why or which part?

Michael Chua · 27th March 2012, 01:36 PM

Haven't worked on this before but a very interesting design. Would I be right to say the 2nd stage current is set by the mirrors. If so, how precise must Q2 and Q3 be.

Am I seeing folded cascodes and cascodes in the 2nd stage?

Bonsai · 27th March 2012, 01:39 PM

I fail to see what this brings over more conventional approaches . . .

AndrewT · 27th March 2012, 01:41 PM

how do I1 & I2 get current from/to the supply rails?
The only route I can see is through the shorted CtoB of Q2 & 3

Edmond Stuart · 27th March 2012, 02:13 PM

Quote:

Originally Posted by Michael Chua

Haven't worked on this before but a very interesting design. Would I be right to say the 2nd stage current is set by the mirrors. If so, how precise must Q2 and Q3 be.

Hi Michael,

Yes, that right, but more precisely, Iq of the 2nd stage (the TIS) is defined by the tail current of the LTPs, which is reflected by the current mirrors.

Quote:

If so, how precise must Q2 and Q3 be.

Well, these transistors should be reasonably matched, just as with any other current mirror.

Quote:

Am I seeing folded cascodes and cascodes in the 2nd stage?

That's also correct, that is, the 'right legs' of the LTPs are 'folded', whereas the 'left legs' are connected via the current mirrors to the TIS.

Cheers,
E.

Bonsai · 27th March 2012, 02:16 PM

So What?

Edmond Stuart · 27th March 2012, 02:17 PM

Quote:

Originally Posted by Bonsai

I fail to see what this brings over more conventional approaches . . .

When I've finished the description on my website and you have read it, I hope you will understand the specific virtues of this circuit .

Cheers,
E.

overtheairbroadcast · 27th March 2012, 02:19 PM

Wow.

You guys are brilliant. Seriously, I just take a look and try to figure out how this works in a rudimentary way (out of interests sake and I have read those recommended books) and then you guys can disect and discuss it in no time flat.

Just something I noticed.

27th March 2012, 12:33 PM	#2
Osvaldo de Banfield diyAudio Member Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina	It is a complementary differential amplifier, but is drawing in a some curious way. __________________ LW1DSE

27th March 2012, 12:50 PM	#3
Edmond Stuart diyAudio Member Join Date: Nov 2003 Location: Amsterdam	>but is drawing in a some curious way Why or which part? __________________ Een volk dat voor tirannen zwicht, zal meer dan lijf en goed verliezen dan dooft het licht…(H.M. van Randwijk)

27th March 2012, 01:36 PM	#4
Michael Chua diyAudio Member Join Date: Jul 2006 Location: Calais, ME	Haven't worked on this before but a very interesting design. Would I be right to say the 2nd stage current is set by the mirrors. If so, how precise must Q2 and Q3 be. Am I seeing folded cascodes and cascodes in the 2nd stage? __________________ AmpsLab.com

27th March 2012, 01:39 PM	#5
Bonsai diyAudio Member Join Date: Aug 2006 Location: Taipei, Taiwan	I fail to see what this brings over more conventional approaches . . . __________________ bonsai Amplifier Design and Construction for MUSIC! http://hifisonix.com/

27th March 2012, 02:16 PM	#8
Bonsai diyAudio Member Join Date: Aug 2006 Location: Taipei, Taiwan	So What? __________________ bonsai Amplifier Design and Construction for MUSIC! http://hifisonix.com/


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27th March 2012, 01:41 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	how do I1 & I2 get current from/to the supply rails? The only route I can see is through the shorted CtoB of Q2 & 3

27th March 2012, 02:19 PM	#10
overtheairbroadcast diyAudio Member Join Date: Jan 2012 Location: Canada	Wow. You guys are brilliant. Seriously, I just take a look and try to figure out how this works in a rudimentary way (out of interests sake and I have read those recommended books) and then you guys can disect and discuss it in no time flat. Just something I noticed.

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