Sziklai pair as Vbe Multiplier?

sam9 · 10th March 2004, 04:24 PM

In his amplifier book near the end of the section on thermal compensation , D.Self describes using a Sziklai pair for the Vbe multiplier. Apart from the possability (probability) that it would oscilate, it has the advantages of very low bias drift and elimination of the trimpot. Self doesn't seem very excited about his own idea.

On Hagerman's website (www.hagtech.com), Hagerman has an article about a "Vbe doubler" with somewhat similar properties although it is not a Sziklai and presumably doesn't have the same oscillation problems.

Has anyone tried to use either of these on a real amp or are they just paper curiosities? Did it work or were there difficulties?

Do either or both of them still require physical contact with output device or heatsink (or driver if CFB)? If yes, do mount both transistors or just one (which)?

If either of these are effective I'm surprised not to have seen anyone attempt to use them.

jam · 10th March 2004, 05:50 PM

The circuit that is on the Hagerman web site has been used by Harmon Kardon and a few others. It still requires that one of the transistors be attached to the heatsink.

Regards,
Jam

sam9 · 10th March 2004, 07:58 PM

Does it matter which one?

jam · 10th March 2004, 08:15 PM

I believe it is the transistor on the right.

sam9 · 10th March 2004, 10:50 PM

Well, looks like the only way to satisfy my curiosity is to try on or another in my next amp project. It looks like I could layout the standard Vbe multiplier and add a couple of componrnts to the PCB so that I could first use a conventional circuit and when I'm satisfied that's stable and working, change component values and add the second transistor. That way I won't be puzzling whether it is the new circuit or something else that causes any problems.

deeps2688 · 14th September 2009, 01:53 PM

I want detal information of sziklai par

juma · 14th September 2009, 05:18 PM

Quote:

Originally Posted by deeps2688

I want detal information of sziklai par

And I want a cherry pie ... now

Mate, use the search button / google is your friend

forr · 14th September 2009, 06:15 PM

Sam9
---In his amplifier book near the end of the section on thermal compensation , D.Self describes using a Sziklai pair for the Vbe multiplier. Apart from the possability (probability) that it would oscilate, it has the advantages of very low bias drift and elimination of the trimpot. Self doesn't seem very excited about his own idea.---

An important advantage of the Sziklai pair for bias control is the lower dynamic impedance compared to a single transistor.

Bigun · 14th September 2009, 08:14 PM

Quote:

Originally Posted by sam9

In his amplifier book near the end of the section on thermal compensation , D.Self describes using a Sziklai pair for the Vbe multiplier.

Has anyone tried to use either of these on a real amp or are they just paper curiosities? Did it work or were there difficulties?

I believe MJL21193 has used this type of multiplier on his Class A 'Nameless' amplifier.

http://www.diyaudio.com/forums/showt...feedback+Class

Scroll down to the schematic in Post 52. He has built it but hasn't had time to debug it yet.

Lumba Ogir · 14th September 2009, 08:46 PM

Gareth,
I wonder if it`s stable...

10th March 2004, 04:24 PM	#1
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Sziklai pair as Vbe Multiplier? In his amplifier book near the end of the section on thermal compensation , D.Self describes using a Sziklai pair for the Vbe multiplier. Apart from the possability (probability) that it would oscilate, it has the advantages of very low bias drift and elimination of the trimpot. Self doesn't seem very excited about his own idea. On Hagerman's website (www.hagtech.com), Hagerman has an article about a "Vbe doubler" with somewhat similar properties although it is not a Sziklai and presumably doesn't have the same oscillation problems. Has anyone tried to use either of these on a real amp or are they just paper curiosities? Did it work or were there difficulties? Do either or both of them still require physical contact with output device or heatsink (or driver if CFB)? If yes, do mount both transistors or just one (which)? If either of these are effective I'm surprised not to have seen anyone attempt to use them.

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10th March 2004, 05:50 PM	#2
jam diyAudio Member Join Date: May 2001 Location: Auburn, CA, USA	The circuit that is on the Hagerman web site has been used by Harmon Kardon and a few others. It still requires that one of the transistors be attached to the heatsink. Regards, Jam

10th March 2004, 07:58 PM	#3
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Does it matter which one?

10th March 2004, 08:15 PM	#4
jam diyAudio Member Join Date: May 2001 Location: Auburn, CA, USA	I believe it is the transistor on the right.

10th March 2004, 10:50 PM	#5
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Well, looks like the only way to satisfy my curiosity is to try on or another in my next amp project. It looks like I could layout the standard Vbe multiplier and add a couple of componrnts to the PCB so that I could first use a conventional circuit and when I'm satisfied that's stable and working, change component values and add the second transistor. That way I won't be puzzling whether it is the new circuit or something else that causes any problems.

14th September 2009, 01:53 PM	#6
deeps2688 diyAudio Member Join Date: Sep 2009	I want detal information of sziklai par

14th September 2009, 06:15 PM	#8
forr diyAudio Member Join Date: Dec 2004 Location: Next door	Sam9 ---In his amplifier book near the end of the section on thermal compensation , D.Self describes using a Sziklai pair for the Vbe multiplier. Apart from the possability (probability) that it would oscilate, it has the advantages of very low bias drift and elimination of the trimpot. Self doesn't seem very excited about his own idea.--- An important advantage of the Sziklai pair for bias control is the lower dynamic impedance compared to a single transistor.

14th September 2009, 08:46 PM	#10
Lumba Ogir Banned Join Date: Apr 2005 Location: Stockholm	Gareth, I wonder if it`s stable...