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Old 18th March 2011, 03:53 PM   #11491
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We buffer with a 2N5564 pair used in follower mode.
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Old 18th March 2011, 03:57 PM   #11492
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Quote:
Originally Posted by hitsware View Post
One might surmise that a 'power' mosfet
would be very quiet due to the statistical
noise cancellation of the thousands of
cells paralleled.
IIRC that was the method used to make this device:
LM394 - SuperMatch Pair [Obsolete]
(only hundreds of bipolar 'cells' in parallel)
From what I remember, these devices are just 4 transistors in a two by two layout, with diagonal bjt's paralleled. I'll see if I can find the die photo, I have it somewhere...

Cheers, John
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Old 18th March 2011, 03:58 PM   #11493
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Quote:
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That should be...

Oh nevermind.

se
.

You can tell I never use the things.
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Old 18th March 2011, 04:04 PM   #11494
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Quote:
Originally Posted by jneutron View Post
From what I remember, these devices are just 4 transistors in a two by two layout, with diagonal bjt's paralleled. I'll see if I can find the die photo, I have it somewhere...

Cheers, John
That's Bob Pease folklore. You can work out mathematically the optimum multi-stripe geometry, it is definately not ordinary 1974 style BJT's in parallel. If it ever was it would have changed due to the waste of silicon. BTW Philips published the derivation and prototyped .2nV BJT's for an AES paper. I have some somewhere but never could afford a MC to use them on. You will also find some amazing BJT's in early magneto-resistive hard drive heads (not discrete).
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Last edited by scott wurcer; 18th March 2011 at 04:07 PM.
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Old 18th March 2011, 04:08 PM   #11495
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The quietest transistor part pair was made by Hitachi starting about 1978. This part pair was amazing, very low Rbb', high beta, high voltage, and complementary. They are talked about here at times, but jfets are really better for most purposes.
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Old 18th March 2011, 04:09 PM   #11496
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> From what I remember, these devices are just 4 transistors
> in a two by two layout, with diagonal bjt's paralleled.
> I'll see if I can find the die photo, I have it somewhere...

If you mean the LM394 then I have the wrong part number.
I remember the spec sheet drawing and the blurb stating
something to the effect of 'statistically matched pair'
I forget the number of xsistors/device, but it was lots.
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Old 18th March 2011, 04:11 PM   #11497
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35? Just a guess.
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Old 18th March 2011, 04:26 PM   #11498
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Quote:
Originally Posted by john curl View Post
The quietest transistor part pair was made by Hitachi starting about 1978. This part pair was amazing, very low Rbb', high beta, high voltage, and complementary. They are talked about here at times, but jfets are really better for most purposes.
Hitachi 2SC2545,46,47 NPN and 2SA1083,84,85 PNP you mean? Toshiba 2SC3329 & 2SA1316 were maybe a wee bit better even.
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Old 18th March 2011, 04:32 PM   #11499
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Tradeoffs, but the Toshiba is certainly a great device.
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Old 18th March 2011, 04:33 PM   #11500
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Quote:
Originally Posted by scott wurcer View Post
That's Bob Pease folklore.
Actually, no. I'm going by memory...used to play with waffle packs and wafers back in the 80's. So I lived dice..

If anything, it's faulty memory. I found some mat-02 stuff on my drive, I may be confusing the two...

[QUOTE=hitsware;2508039If you mean the LM394 then I have the wrong part number.
I remember the spec sheet drawing and the blurb stating
something to the effect of 'statistically matched pair'
I forget the number of xsistors/device, but it was lots.[/QUOTE]

I'm not sure, but I think the 194 and 394 are just different grades of the same die.

But I'n not sure if this is the die I'm thinkin of however..

Cheers, John
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