Any suggestion for a decent input JFET pair?

[PMA]

I am searching for a decent JFET input pair, it would operate with drain current between 1 - 2 mA. I have not worked with JFETs that much, so any suggestion would be greatly appreciated. It should be an available type.

 

[MikeB]

Hi Pavel,

I could recommend the 2sk170, at www.schuro.de you get them for a
reasonable price, original Toshiba-devices. (That's where i bought them)
The sk170 has max Vds of 40v, and i already used it in several designs,
without any problems. It has at least the transconductance of a "poor" bjt...
The 2sk389 is also interesting, it's a double device, i have some but not
used yet, so i don't know how good the matching is.

Mike

 

[bocka]

The 2sk389 is also interesting, it's a double device, i have some but not

Similar to OPs! Offset voltage is some mV

 

[PMA]

Forgot to say that I need N-JFET + P-JFET

Hi Michael nad bocka,

thank you for your recommendations. I forgot to say that I need a couple of different conductivity, i.e. N-JFET + P-JFET.

Pavel

 

[jacco vermeulen]

Pavel,

the partner of the 2SK170 is the 2SJ74, 2.5 times more pricy though.

 

[MikeB]

Okay, in this case, 2sk170 + 2sj74 !
But the 2sj74 has max Vds of only 25v...
I've build complementary circuits using these 2, worked fine !

Mike

 

[PMA]

Thank you jacco and Mike, I will download datasheets and review these components.

 

[jacco vermeulen]

to check for pairs :
http://www.geocities.co.jp/Technopolis/4999/main/tr_data.txt

Dalbani in the UK still has some of the complementary pairs.

 

[aparatusonitus]

If you are going to use 2SK389 in complementary topology, then you also need 2SJ109.

OT - Could you show as a balance version schematic of your error correction amp, as you promise long time ago (if i'm not mistaking), thank you.

Best, a

 

[PMA]

I
OT - Could you show as a balance version schematic of your error correction amp, as you promise long time ago (if i'm not mistaking), thank you.

Best, a

I am afraid there is not much to say about it, 2 identical modules connected as follows:

 

[lumanauw]

Hi, PMA,

You can look at www.linearsystems.com. They have twin fet in a 8dip (IC) package. K389 and J109 seems are out of production now.

 

[helan]

Hi Pavel,

other useful complementary Toshiba types:

2SJ103/2SK246 (TO-92, PD 300mW) or (the same chips)
2SJ105/2SK330 (MINI, a smaller TO-92 variant PD200mW)

Both P-Ch. and N-Ch. with Vgds 50V. Less Yfs, less Ciss but
higher VGS(OFF) than 2SJ74/2SK170.

Regards

Ole

 

[MikeB]

Hi helan,
The sk330 is not too useful for amplifying, it has 5 times less transconductance
than the sk170, this makes it more useful for buffers or ccs !

Pavel, what do you need the jfets for ?

Mike

 

[PMA]

Mike,

not for the SymAsym. Let me be a bit mysterious please

Pavel

 

[MikeB]

not for the SymAsym. Let me be a bit mysterious please

Okay, i was sure that it was not for symasym, because of the complementaries...
But, now, i got really CURIOUS !!!

Mike