How critical is matching PNP/NPN in complementary stages?

[nelsonvandal]

It's hard and expensive to acquire complementary transistor pairs. How critical is it in driver and output stages to find perfectly matched pairs? Is it worth the effort?

[Nico Ras]

Originally posted by nelsonvandal
It's hard and expensive to acquire complementary transistor pairs. How critical is it in driver and output stages to find perfectly matched pairs? Is it worth the effort?

If I may be very honest, and I am not trying to be a smart guy.

I do not match at all anymore (I also use a lot of NFB). If all electronic manufacturers had to match transistors for every application then we would be throwing away 99% of all components, or we would be employing thousands of people matching semiconductors to keep up with the high speed pick and place machines, and things would cost considerably more than they do now.

Modern manufacturing technologies used in producting semiconductors have improved considerably since their incepion in the 50's. If transistor matching or their models were so bad from manufacturers, they may as well print random numbers on them.

Nico

[nelsonvandal]

The spread within one batch of transistors is often very small, but the difference in Hfe between the complementary PNP and NPN is often 2 - 3 times.

[AndrewT]

PMA said in this thread http://www.diyaudio.com/forums/showt...88#post1690588

It is all about distortion cancellation in input complementary-differential stages, exact BJT PNP-NPN matching.......

whereas many other builders/designers say that matching between N & P is not particularly important.
However, parallel devices do show benefits in careful close matching.
An LTP benefits even more with precise matching.

[nelsonvandal]

So regarding output transistors in a push-pull stage, you can get away using a PNP with Hfe of 300 and an NPN with Hfe 100?

[destroyer X]

those ones use a PNP Differential and a NPN differential...alike Leach amplifier...if you do not match you perceive bad sound.

It is hard to match them.... maximum i could, my whole life was to mach PNP and NPN into a 12.5 percent range... they had always difference in gain.

Now a days i do not care about anymore... i accept that is hard and them i avoid double differential and things that needs such kind of matching.

But i know that i am not doing the best possible job accepting the mismatching.

And if this sounds or do not sound is not more important...if you feel that something is not correct you will always feel unsafe about the amplifier performance...you will always ask yourself:

- "And if was matched?... would be better than that?"

So... the problem goes inside our intimate psychology... the problem goes from technicall to psychological... you do not feel safe to say it is good or bad...not perfeclty assembled!

regards,

Carlois

[Lumba Ogir]

Nelson,
you have no control over most characteristics. Matching as a result of die design and manufacturing precision is much more important. PNP has necessarily poorer characteristics. And again, you cannot cure the main problem of the signal waveform being amplified by essentially two different parts.

[Nico Ras]

Originally posted by destroyer X

those ones use a PNP Differential and a NPN differential...alike Leach amplifier...if you do not match you perceive bad sound.

It is hard to match them.... maximum i could, my whole life was to mach PNP and NPN into a 12.5 percent range... they had always difference in gain.

Now a days i do not care about anymore... i accept that is hard and them i avoid double differential and things that needs such kind of matching.

But i know that i am not doing the best possible job accepting the mismatching.

And if this sounds or do not sound is not more important...if you feel that something is not correct you will always feel unsafe about the amplifier performance...you will always ask yourself:

- "And if was matched?... would be better than that?"

So... the problem goes inside our intimate psychology... the problem goes from technicall to psychological... you do not feel safe to say it is good or bad...not perfeclty assembled!

regards,

Carlois

Hi Carlos,
I agree with you totally. I am getting too old to sit and measure transistors. I rather build it and listen. If I like it then I may make some efforts. But like you I want to get a result quickly with my ears.
I think the human ear cannot tell whether a wave is symetrically placed around 0V.

Nico

[clm811]

Assembling 10 device Leach clone boards now, and have a question about the 2nd stage and driver transistors.

Out of the several MJE340/350 transistors that we have in our group, some are made by Fairchilds and some by ON Semi.

I notice some fairly close matches were found(using a multimeter) between a few ON semi JE340(NPN) and Fairchild MJE350(PNP) devices.

So, my question is:

In this application (Leach clone at locations T8,T9,T13,T14), would it be better to have:

a) Complementary devices (PNP and NPN) with widely different hFE from the same manufacturer,
or
b)Complementary devices(PNP and NPN) with similar hFE, each from a different manufacturer?

Is it worth it to mix and match brands like that, is it a bad idea, or is all this a complete waste of time?

Thanks for tolerating such questions from us "noobs"

-Chas

[Jan Dupont]

In this application (Leach clone at locations T8,T9,T13,T14), would it be better to have:

a) Complementary devices (PNP and NPN) with widely different hFE from the same manufacturer,
or
b)Complementary devices(PNP and NPN) with similar hFE, each from a different manufacturer?

Is it worth it to mix and match brands like that, is it a bad idea, or is all this a complete waste of time?

Different brands of the same BTJ "should" be within the same tolerances (if not fakes).
And as also said in this and many other threads here, there are major differences between complementary NPN and PNP devices from the same manufacturer.
As one of the main factors is Hfe matching, I go for this and mixing brands if needed.