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Old 9th January 2012, 03:09 AM   #1
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Unhappy Matched n-channel JFET

No doubt this comes up from time to time, but what the heck happened to JFETs while I was sleeping? One minute they're cheap and easily available, the next, only the 2n3819 and similar seem left.

I'm searching for a monolithic matched pair for my own design, preferably one that I can get this time next year! Low noise is they key here, so mos won't do... I could use bipolar but jfet gets that sound you don't get with bipolar.

Any suggestions gratefully received - preferably ones that won't require the sale of internal organs...
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Old 9th January 2012, 03:56 AM   #2
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Linear Systems LSK389 comes to mind.

Toshiba have discontinued almost everything of interest from their discretes catalog. Slim pickings ahead it seems..

-Len.
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Old 9th January 2012, 01:47 PM   #3
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Yes... Very slim. At this rate I'll have to go any buy a box of MPF102s and sort some matched pairs myself. I know FETs have their problems, but it's a shame that they're being abandoned in preference for single chip solutions like Op Amps.

The circuit I had in mind was suggested by Horowitz and Hill and only needs 2 pairs. The same thing with Op Amps needs at least three amps and would be better with more. Now that's a pain because all the extra silicon adds noise and isn't optimised for what I need.
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Old 9th January 2012, 07:19 PM   #4
juma is offline juma  Serbia
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BF862
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Old 11th January 2012, 12:08 AM   #5
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Thanks juma, but that's a single. I need two on the same bit of silicone.

Cheers anyway,

Marc
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Old 11th January 2012, 08:46 AM   #6
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I also worry a bit about the low interest for matched transistors among manufacturers. This is not a JFET, but a depletion mode MOSFET, kinda similar. Advanced Linear Devices makes some interesting matched transistors, duals and quads. Mostly low voltage devices, but that just gives us a good excuse for a cascode.
http://www.aldinc.com/pdf/ALD114804.pdf
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