FET Matcher

slideman82 · November 21, 2007, 06:44:54 PM

Well, I tried to compare the Fet matcher of Geofex and the one from ROG... the last one always worked, but the one from Geofex doesn't seem too... has anyone has troubles with it?

Barcode80 · November 21, 2007, 06:51:50 PM

am i dense or missing something? i don't see a fet matcher on ROG.

slacker · November 21, 2007, 06:59:17 PM

Quote from: Barcode80 on November 21, 2007, 06:51:50 PM
i don't see a fet matcher on ROG.

There's notes and schematics for measuring FETs on the Fetzer valve page, I guess that's what he's talking about.

I've used the Geofex one a few times, it works fine. I'd double check you've built it correctly.

slideman82 · November 21, 2007, 07:01:14 PM

Yeah, I think you're right.... Laaaaaaaaaaaaaaaaaaaazy stay in bed!

Papa_lazerous · November 21, 2007, 07:23:06 PM

I have used the FET mather from GEOfex works perfectly

oldrocker · November 21, 2007, 10:24:13 PM

Yes the fet matcher at the Geo site is the one I used. When I need to match fets I breadboard the Geo fet matcher and start matching. It worked great for my Phase 45.

Barcode80 · November 22, 2007, 12:53:00 AM

yeah i just finished up a phase 45 and i went ahead and committed the matcher at GEO to vero, as i plan on building a few more phasers. good stuff.

96ecss · November 22, 2007, 01:07:04 AM

I did a pcb layout for the Geo Fet matcher. It works fine.

Dave

Barcode80 · November 22, 2007, 02:27:39 AM

here is mine:

oldrocker · November 22, 2007, 02:29:57 AM

The Microsoft mouse jfet matcher is really cool. Great idea.

MartyMart · November 22, 2007, 04:50:27 AM

Thats the best use of a Microsoft product that 've EVER seen !!!!

Plinky · November 22, 2007, 12:25:34 PM

Does it work all the time, unlike most MS products???

Barcode80 · November 22, 2007, 09:38:49 PM

Quote from: Plinky on November 22, 2007, 12:25:34 PM
Does it work all the time, unlike most MS products???

well, i occasionally have to restart it... and it doesn't support ALL dmm's

mac · November 23, 2007, 12:13:27 AM

I use Geo matcher, but I test for different values of Rset, 1k to 22k in a P45/90.

Quote
Does it work all the time, unlike most MS products???
well, i occasionally have to restart it... and it doesn't support ALL dmm's

Use a Mac mouse.

mac

Barcode80 · November 23, 2007, 01:15:11 AM

hmm, i wonder if i am doing something wrong. everyone else seems to get less than a volt of negative voltage when matching, i usually get around 3!

stm · November 23, 2007, 07:08:23 AM

Quote from: Barcode80 on November 23, 2007, 01:15:11 AM
hmm, i wonder if i am doing something wrong. everyone else seems to get less than a volt of negative voltage when matching, i usually get around 3!

Seems all is good. Different JFETs have different typical valoes for VGSoff (or equivalently Vp).

Values less than one volt (negative) are typical of J201's, while values as high as -3V are typical of MPF102's and 2N5459's.

R.G. · November 23, 2007, 12:01:05 PM

Correct, stm.

In fact, I believe the MPF102 can be as much as -8V and still be in spec. Some JFETs have Vgsoff as much as -15V and can only be used in 9v designs with great care.

Barcode80 · November 23, 2007, 02:52:21 PM

okay cool. i had like 10 2n5452's and when i started testing they were all in the 3 range and were REALLY close to matched already. must have been all from the same batch.

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FET Matcher