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Old 15th February 2003, 04:25 PM   #1
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Question LM 394 Supermatch Pair

Mornin',

I searched the site under a few different strings and have come to the conclusion that there has not been any discussion concerning National's LM394 Supermatch Pair. I was wondering if anybody had tried them in place of the dual-monolithic Toshiba N-type BJT's or JFET's?

A friend of mine who is a Bob Pease fan, turned me on to them after having read an article Bob wrote concerning a simple yet accurate AC watt meter published in Electronic Design. We were looking for an alternative part so we began looking at the spec's for the LM394 to determine if we had anything like it already. It's impressive to say the least. I'm just wondring if there are any peculiarities that may make it undesirable for audio, besides violating one of Jocko's laws--TO-5 case.

I am inclined to think that it would make a wonderful differential input pair. Check out the .pdf file and let me know what you think.

Later,
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Old 15th February 2003, 04:54 PM   #2
SY is offline SY  United States
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Supermatch pairs can be useful in instrumentation work. As for audio, I used them in the input stage of a power amp I built some time ago and they worked fine. No better, for that application, than a normally matched pair, but they had the virtue of being free.

There's probably not much discussion of them because of their age: available for at least 25 years now, the 194/394 family is not in any way exotic. I haven't kept up with that literature since my instrumentation days, but I'll bet there's all kinds of supermatch pairs out there these days with better specs.
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Old 15th February 2003, 05:00 PM   #3
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LM394 is allright I guess (when it's used right). You could also check MAT01 and MAT02/03

http://search1.analog.com/searchProx...queryText=MAT&
http://www.analog.com/Analog_Root/pr...53D0%2C00.html

and

http://www.thatcorp.com/
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Old 15th February 2003, 06:53 PM   #4
halojoy is offline halojoy  Sweden
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Default Re: LM 394 Supermatch Pair

Quote:
Originally posted by stadams
I searched the site under a few different strings and have come to the conclusion that there has not been any discussion concerning National's LM394 Supermatch Pair. I was wondering if anybody had tried them in place of the dual-monolithic Toshiba N-type BJT's or JFET's?
Great stadams!
When you mention this LM394 pair, I remembered an application I studied some years ago and found very interesting.

A very low noise and rather simple preamp.
So now I have searched and found that little amplifier.
It is from the same link you provided,but in applications.

http://www.national.com/pf/LM/LM394....cation%20Notes

AN-222: Application Note 222
Super Matched Bipolar Transistor Pair
Sets New Standards for Drift and Noise

Of course it is some years ago this was published first.
But the noise is no higher in this amp, maybe there are alternatives nowadays that are better.
But not much better and certainly not as simple.
----------------------------------------------------------------

/halo - the guy with low bipolar noise
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Old 15th February 2003, 06:55 PM   #5
halojoy is offline halojoy  Sweden
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Thumbs up Here is the Schematic of this Super Low noise Amplifier

Quote:
An ideal application for this amplifier is as a head pre-amp
for moving-coil phono cartridges. These cartridges have very
low output impedance (< 50 Ohm at low frequencies) and have
a full-output signal below 1 mV. Obviously, the preamp used
for such a low signal level must have superb noise proper-ties.
The amplifier shown has a total RMS input noise of
0.11 uV in a 20 kHz bandwidth, yielding a signal-to-noise
ratio of 70 dB when used with a 40 Ohm source impedance at a
0.5 mV signal level.
Attached Images
File Type: gif lm394_lownoisepre.gif (20.2 KB, 557 views)
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Old 15th February 2003, 08:10 PM   #6
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Halo, this amp was cool 15 years ago. LM394 has low noise but there are better types now. Even an opamp is better, if we talk noise.

MAT02/02 and "Thats" are better.
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Old 15th February 2003, 08:41 PM   #7
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by peranders
Halo, this amp was cool 15 years ago. LM394 has low noise but there are better types now. Even an opamp is better, if we talk noise.
MAT02/02 and &quot;Thats&quot; are better.
That was what I thought.
Still how many transistors are there in an OPamp?
And there is nothing to stop us from using MATxx
in the same configuration. Not that I can see.
And we could learn something from most different configurations.

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