2SJ109 Available

I received a flier from MCM electronics and noticed they have 2SJ109 FETs, the compliment to 2SK389, "on sale" for $3.24. Since I read in another thread that these were rare, I just thought I would mention it. MCM link:http://www.mcmelectronics.com/

They and the 389s have been discontinued by Toshiba, with only the 389 being done as an approximate replacement by Linear Integrated Systems.

There's probably a lot less NOS on the 109, since it was never as widely used as the 389.

Do they make the 389 already? Last time I looked I didn't found anything on the webpage?

Samuel

yeah me too... i've been waiting for a replacement for those... :thumb:

[quote author="Samuel Groner"]Do they make the 389 already? Last time I looked I didn't found anything on the webpage?

Samuel[/quote]

It was supposed to be out by now but evidently there has been a delay.

My last word from them was on 14 Feb 2005:

Brad,

The parts will be announced
in March.

The VGS1 - 2 will be 5 - 10mV
with good temp coefficient.
The interdigitation also helps
reduce the noise.

Don

What equipment are these Fets used in ? (ex : U87 mic)

[quote author="maxwall"]What equipment are these Fets used in ? (ex : U87 mic)[/quote]

I don't know of much of anything commercial. Some fair amount of time ago they may have been in Japanese consumer equipment, for MC phono inputs.

There's not much need for a dual in a condenser mic, at least with typical designs. The d.c. offset matching is not needed, and the use as a differential pair will give 3dB more series noise, all other things equal.

Even Erno Borbely, the prominent apostle of Toshiba FETs, seems to usually prefer matching individual 2SK170's and 2SJ74's, possibly because of the absence of substrate capacitance and cross-coupling. Also the individual parts are somewhat lower noise than each half of the duals.

I'm going to use the 389 in a highend crossover product soon, but I haven't seen the need for the 109 complement as yet.