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Stefanoo 2nd January 2007 01:49 PM

how to match devices -help-
I'm searching on the forum how to match transistor-jfet-mosfet.

I would like to know...if it is possible do it on your own.
If so, is there any circuit test that i can build and that work fine for the purpose?

hope to receive everytime...your good advice!

best regards,

moe29 2nd January 2007 02:50 PM

which FETS are you trying to match?

is there a particular amp you are going to build?

Check out and under the Articles section there is a paper on matching FETS.

Stefanoo 2nd January 2007 03:08 PM

well actually i have to repair my electrocompaniet ECI-4 and i have to replace the transistor (driver and output stage).
Since the configuration is in differential i would like to replace...since i'm have to....with complementary matched type.

The devices that i have to match are BJT (motorola MJL3281A and 1302A and Toshiba 2sa1350y and 2sc3421y).....which i still have to find somewhere...and i hope somebody could help me.

I also found them on the they since to supply only the industries.

x84andrea 2nd January 2007 03:33 PM

ciao, parliamo in italiano! basta che gli mandi una corrente fissa e calcoli la differenza di potenziale con il mos collegato a diodo,
puoi usare un lm317 in modalita sorgente di corrente e fare le misurazioni, mandagli 500ma o pił!
per fare questo devi dissipare il317 e il mos, se vuoi altro fammi sapere a

carpenter 2nd January 2007 03:33 PM

If you're talking about basic VGS matching, I saw suggestions in Nelson's DIY op amp article. I have a drawing if you want it.

GRollins 2nd January 2007 03:51 PM

Since they're bipolars, Vgs isn't applicable, unfortunately. That's for FETs. The equivalent measurement for bipolars--Vbe--is quite consistent.
What parameter needs to be matched? Beta? If so, to what spec?


carpenter 2nd January 2007 05:15 PM


I'm searching on the forum how to match transistor-jfet-mosfet.
I guess this kind of threw me.:)

DIY op amps also shows how to match bipolars.

Stefanoo 3rd January 2007 06:39 AM

thanks guys for the posts.
I would like to have a little circuit test for matching Bipolar Transistor (mostly) and also have a circuit ...that i guess it's different... for MOS and FET.

I mean.....what do the companies use for selecting their componens? does anybody know it?

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