Hi All.
So I managed to source a few toshiba 2sj109 BL.
I realize that there's probably a lot of fakes around out there, but I bought from what seems to be a decent dealer so I have some small hope...
I won't name them at this stage, not until I'm sure one way or the other.
Now, I am a complete n00b when it comes to jfets, so I grabbed the data sheet:
http://ezphysics.nchu.edu.tw/prophys/ael/File/Datasheet/2sj109.pdf
and did a quick measurement of IDSS.
The part came up as 10ma, which looked promising, but I have a couple of concerns, both about my results, and methods
So is this right?:
I have the Gate and Source connected (Vgs=0V) and I am putting 10 V from Source to Drain (Vds = -10V).
Then I measure the current Ids.
Is this right?
The other concern I have is that if I am reading the datasheet properly, Ids shouldn't vary much as I change Vds from say -2V to -10V.
This is where things get interesting, as I am measuring around 6ma at -4V which steadily increases to 10ma at -10V.
Should it vary this much?
I'm trying to avoid plotting curves...
Any thoughts?
Mark
So I managed to source a few toshiba 2sj109 BL.
I realize that there's probably a lot of fakes around out there, but I bought from what seems to be a decent dealer so I have some small hope...
I won't name them at this stage, not until I'm sure one way or the other.
Now, I am a complete n00b when it comes to jfets, so I grabbed the data sheet:
http://ezphysics.nchu.edu.tw/prophys/ael/File/Datasheet/2sj109.pdf
and did a quick measurement of IDSS.
The part came up as 10ma, which looked promising, but I have a couple of concerns, both about my results, and methods
So is this right?:
I have the Gate and Source connected (Vgs=0V) and I am putting 10 V from Source to Drain (Vds = -10V).
Then I measure the current Ids.
Is this right?
The other concern I have is that if I am reading the datasheet properly, Ids shouldn't vary much as I change Vds from say -2V to -10V.
This is where things get interesting, as I am measuring around 6ma at -4V which steadily increases to 10ma at -10V.
Should it vary this much?
I'm trying to avoid plotting curves...
Any thoughts?
Mark
2sj109 is a pchannel jFET.
Vgs is +ve when measured from G to S.
Id varies a lot as Vds is varied.
i.e. expect >50% variation in Id as Vds is swept from -2V to -10V
This is why we put a low gm jFET around the j109 as a cascode to nearly eliminate the variation in Id as the supply voltage is varied.
Vgs is +ve when measured from G to S.
Id varies a lot as Vds is varied.
i.e. expect >50% variation in Id as Vds is swept from -2V to -10V
This is why we put a low gm jFET around the j109 as a cascode to nearly eliminate the variation in Id as the supply voltage is varied.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.