while I was typing and preparing sch , several posts showed 
definitely fake Jfets
try to find 2SJ74BL , or buy J271 , few dozens , and match them by your self
definitely fake Jfets
try to find 2SJ74BL , or buy J271 , few dozens , and match them by your self
if I test theJfets with a fresh 9V baterry(idss measurement) the dmm reads 60ma and goes down slowly the fet is getting hot quickly, if the battery is used the dmm starts from 15ma and goes down to 8ma in 5 minutes and still goes down..
i will measure voltages in few minutes and be right back
i will measure voltages in few minutes and be right back
I have found on ebay at alweit 2 pairs of J74BL at these matching specs : 2 very well matched pairs: I declare +/-2% to be on a safe side but really I select no more than +/- 1% (Vgs = 10V) - really, I allow maximum difference between pair is 0.03 mA(I know the matching between channels isn't necesary)
and spencer has this specs : As in the past, the match from part to part is within 0.2mA assurance but you will get normally within 0.1mA tolerance. The Idss accuracy is about +/-0.1mA due variation of equipment and temperature during test. Special requirements may or may not be fullfilled and it is a case by case discussion.
Guess the first ones are the best, right?
and spencer has this specs : As in the past, the match from part to part is within 0.2mA assurance but you will get normally within 0.1mA tolerance. The Idss accuracy is about +/-0.1mA due variation of equipment and temperature during test. Special requirements may or may not be fullfilled and it is a case by case discussion.
Guess the first ones are the best, right?