Need help by replacing the dual jfet 2SJ109

[karnevil9]

Has anybody an idea what part I could use to replace the dual p-channel jfet 2SJ109. It's designed for low noise, low drift audio-input-stages. It seems that this part is discontinued by toshiba.

 

[tangent]

Linear Integrated Systems has a few Toshiba dual JFET replacements that may be suitable. They're not pin compatible, but with a little creative lead bending...

 

[Pars]

Quote:

Originally Posted by karnevil9 Has anybody an idea what part I could use to replace the dual p-channel jfet 2SJ109. It's designed for low noise, low drift audio-input-stages. It seems that this part is discontinued by toshiba.

Check with head-fi member dgardner who has some of these in stock and for sale. Alternately, the single FET for this part is a 2SJ74 (IIRC, check on this and perhaps do a search here). You would need two of these to replace the dual 2SJ109, and you would need to match them.

Quote:

Originally Posted by amb Pars, the separate versions are 2SK170 (N-channel) and 2SJ74 (P-channel). Since these are not formed on the same substrate you will see much more variations in Idss between units. To get good matches might require a fairly large number of them and a lot of time to test.

Did the search for you...

 

[amb]

Quote:

Originally Posted by tangent Linear Integrated Systems has a few Toshiba dual JFET replacements that may be suitable. They're not pin compatible, but with a little creative lead bending...

They don't currently have P-channel equivalents of these devices. If they did I'd be using them for my new β22 amp, no question...

 

[karnevil9]

Thank you for that Info. So I have to by some 2SJ74 and try to match them. I think I have to match two parameters: Id and S, am I right? I hope the temperature drift will be suitable for a voltage gain of 1000.

 

[amb]

Quote:

Originally Posted by karnevil9 Thank you for that Info. So I have to by some 2SJ74 and try to match them. I think I have to match two parameters: Id and S, am I right? I hope the temperature drift will be suitable for a voltage gain of 1000.

Just maching the Idss should be sufficient.

 

[Whit]

Quote:

Originally Posted by amb They don't currently have P-channel equivalents of these devices. If they did I'd be using them for my new β22 amp, no question...

Linear Systems is planning to release their version of the 2SJ74 and 2SJ109 later this year or early next year.

 

[amb]

Quote:

Originally Posted by Whit Linear Systems is planning to release their version of the 2SJ74 and 2SJ109 later this year or early next year.

Hmm. I talked to one of their engineers a few months ago and he told me that the 2SJ74 is planned, but not the 2SJ109. Maybe they have finally seen the light! I am curious where you got this info?

If true, then this is good news, perhaps these parts will hit the market just as the β22 project gets wrapped up. Too bad the dual FETs are only "functionally equivalent" but not physically (i.e., you design the PCB for the Toshiba version or the Linear version, but not both).

 

[jar]

If accurate, that's great news for the dynalo people once dan's supply runs out. Why would Linear not make them pin compatible? Seems stupid to me, unless they get kickbacks from layout guys or own stock in some PCB houses.