Linearizing diodes in amp circuits.

Acoustic Absorb · 19th August 2006, 03:23 PM

Greetings.
Are linearizing diodes ever used to linearize the transfer characteristic of transistors in audio amps? I haven't seen any examples in the schematics. Google indicates that the technique is used in RF amps and diode lasers, but no examples in audio amps that I can find. Is there any role for them? what are the difficulties in using the technique? Are there any casualties among you from attempts to make it work? I look forward to your views with interest.

lumanauw · 19th August 2006, 04:29 PM

Quote:

Are linearizing diodes ever used to linearize the transfer characteristic of transistors in audio amps

Where to put diode in the transistor? You got example drawing?

davidallancole · 19th August 2006, 04:59 PM

Take a look at this:

http://ca.search.yahoo.com/search?p=...-web-t912&b=11

Go to number 12.

lumanauw · 19th August 2006, 05:45 PM

It is LM13600

Is the linearizing diode is D2 and D3? What are they doing there? What's the mechanism to obtain the "linearizing"? Won't the DC offset annoyed?

Acoustic Absorb · 19th August 2006, 06:21 PM

>Where to put diode in the transistor? You got example drawing?

I haven't sketched any examples yet. I will study the examples referenced in the reply from member lumanauw before spending time on it. I am putting off working on this idea in case there are some compelling reasons to avoid it.

Acoustic Absorb · 19th August 2006, 06:32 PM

>Take a look at this:
>http://ca.search.yahoo.com/search?p...b-web-t912&b=11
>Go to number 12.

There is plenty of material to study there. I am still curious why there are no examples of discrete amps using linearizing diodes.

I expect it is easier use them in ICs due to better matching of diode and transistor properties when they are on the same die.

Acoustic Absorb · 19th August 2006, 06:37 PM

>Where to put diode in the transistor? You got example drawing?

I expect I would use them to linearize the input transistors which give voltage gain. Small signal transistors; FETs and tubes all seem to have a non linear transfer characteristic and so there might be a role for linearizing diodes. This would be an alternative to high open loop gain with feedback to achieve linearity.

darkfenriz · 19th August 2006, 06:53 PM

You can "linearize" current driven common emitter stage to current mirror. You will get lower gain, but better linearity. Good basic example?

john curl · 19th August 2006, 10:51 PM

Very hard to do right, except by experts.

latala · 19th August 2006, 11:00 PM

The first think that comes to my mind is the baxendall diode as used inthe Linsey Hood 75 watt design ! This is used to match the transfer characteristics between the quasi-complimentary output stage transistors !
A similar technique is also used in the old Phase linear 400/700 power amps
Regards Trev

19th August 2006, 03:23 PM	#1
Acoustic Absorb diyAudio Member Join Date: Mar 2006 Location: Ireland	Linearizing diodes in amp circuits. Greetings. Are linearizing diodes ever used to linearize the transfer characteristic of transistors in audio amps? I haven't seen any examples in the schematics. Google indicates that the technique is used in RF amps and diode lasers, but no examples in audio amps that I can find. Is there any role for them? what are the difficulties in using the technique? Are there any casualties among you from attempts to make it work? I look forward to your views with interest.

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19th August 2006, 04:59 PM	#3
davidallancole diyAudio Member Join Date: Nov 2005	Take a look at this: http://ca.search.yahoo.com/search?p=...-web-t912&b=11 Go to number 12.

19th August 2006, 06:21 PM	#5
Acoustic Absorb diyAudio Member Join Date: Mar 2006 Location: Ireland	>Where to put diode in the transistor? You got example drawing? I haven't sketched any examples yet. I will study the examples referenced in the reply from member lumanauw before spending time on it. I am putting off working on this idea in case there are some compelling reasons to avoid it.

19th August 2006, 06:32 PM	#6
Acoustic Absorb diyAudio Member Join Date: Mar 2006 Location: Ireland	>Take a look at this: >http://ca.search.yahoo.com/search?p...b-web-t912&b=11 >Go to number 12. There is plenty of material to study there. I am still curious why there are no examples of discrete amps using linearizing diodes. I expect it is easier use them in ICs due to better matching of diode and transistor properties when they are on the same die.

19th August 2006, 06:37 PM	#7
Acoustic Absorb diyAudio Member Join Date: Mar 2006 Location: Ireland	>Where to put diode in the transistor? You got example drawing? I expect I would use them to linearize the input transistors which give voltage gain. Small signal transistors; FETs and tubes all seem to have a non linear transfer characteristic and so there might be a role for linearizing diodes. This would be an alternative to high open loop gain with feedback to achieve linearity.

19th August 2006, 10:51 PM	#9
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Very hard to do right, except by experts.

19th August 2006, 11:00 PM	#10
latala diyAudio Member Join Date: Feb 2006 Location: staffordshire	The first think that comes to my mind is the baxendall diode as used inthe Linsey Hood 75 watt design ! This is used to match the transfer characteristics between the quasi-complimentary output stage transistors ! A similar technique is also used in the old Phase linear 400/700 power amps Regards Trev

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