Hi,
I need to build a current source of around 1-5mA. Could anyone suggest some low noise JFET which can do the job and most importantly they are currently available on mouser?
I need to build a current source of around 1-5mA. Could anyone suggest some low noise JFET which can do the job and most importantly they are currently available on mouser?
My version of the G = 1000 low noise measurement amp (for Ikoflexer).
That and the few surounding posts have some info on Sanyo/Fairchild/Onsemi/? jfet parts
That and the few surounding posts have some info on Sanyo/Fairchild/Onsemi/? jfet parts
IF140, 2N4867 -> 2N4869, 2N6451 -> 2N6454 and many more from InterFet including pairs
2SK3557 on semicon
Ssm2212 double low noise bjt matched to 0.5%
2SK3557 on semicon
Ssm2212 double low noise bjt matched to 0.5%
You can still get the 2SK209, which is the SMD version of the 2SK117. It has only slightly higher en than a 2SK170 but about a third of the capacitance.
Hi,
the combination of a 2N/PN/MMBF 4393 with a 4392 or 4391 could do the job.
They come in different flavours, i.e. casings and from different manufacturers.
jauu
Calvin
the combination of a 2N/PN/MMBF 4393 with a 4392 or 4391 could do the job.
They come in different flavours, i.e. casings and from different manufacturers.
jauu
Calvin
Why not LSK170 or LSJ74? Diyaudiostore sells both in matched pairs and in packs of 8. They're sold out of all their JFETs at the moment, but they always get more. Ebay typically has a few pretty reliable sources for the original Toshiba parts.
Hi,
maybe simply because they are not intended for current source useage in first place?
The capacitances are higher than wished for for a CCS.
Btw. the 4393 -4391 are still available in TH as well as SMD.
jauu
Calvin
maybe simply because they are not intended for current source useage in first place?
The capacitances are higher than wished for for a CCS.
Btw. the 4393 -4391 are still available in TH as well as SMD.
jauu
Calvin
> Btw. the 4393 -4391 are still available in TH ....
Which one you meant ?
2.5€ from Central, or 13€ from Interfet ?
You have noise measurements of those ?
Cheers,
Patrick
Which one you meant ?
2.5€ from Central, or 13€ from Interfet ?
You have noise measurements of those ?
Cheers,
Patrick
Apparently 3nV/sqrtHz :
http://www.linearsystems.com/lsdata/datasheets/201181 - 4391DFN SERIES Rev A7 dated 2018 01 31.pdf
Cheers,
Patrick
http://www.linearsystems.com/lsdata/datasheets/201181 - 4391DFN SERIES Rev A7 dated 2018 01 31.pdf
Cheers,
Patrick
can you use a low capacitance device for the cascode ?
the cascode device doesn't contribute much noise, so you can choose based on capacitance
with the cascode, the ccs device underneath doesn't have dynamic voltages, so the capacitance is much less important
or am i missing something??
"with the cascode, the ccs device underneath doesn't have dynamic voltages, so the capacitance is much less important"
What's more is those cascode devices present a low impedance to the capacitance underneath it. The designer doesn't have to care about the capacitance of large die matched transistors.
What's more is those cascode devices present a low impedance to the capacitance underneath it. The designer doesn't have to care about the capacitance of large die matched transistors.