Hi All - I bought a pack of 10 "sj74"'s recently from China, with a limited expectation of getting real parts. I've a Mini Aleph-J I'm halfway through building and getting appropriate jfets is proving a sticking point.
I did a quick test on a few of them (ala Borbely's jets articles - attached) and came up with the following results... Note I used a virtual ground provided by a pair of 1K5 resistors across a 20V supply, as opposed to dual supplies of 10V
#1 Vp= -1.20V, Vgs @2mA = -335mV, Vgs @ 5mA = 106mV
#2 vp= -1.05V, Vgs @2mA = -294mV, Vgs @ 5mA = 158mV
#3 Vp= -1.55V, Vgs @2mA = -398mV, Vgs @ 5mA = 42.7mV
First time I've done this, so if there's any glaring errors, please mention it... other than the fact that as I understand it these aren't sj74's as I understand how to interpret the results.
So, my question to you all - what are they? And can I actually still use them in a mini AJ?
Addendum - I have a pile of J174's headed my way as a potential substitute... pending my learning to use them in that particular circuit!
I did a quick test on a few of them (ala Borbely's jets articles - attached) and came up with the following results... Note I used a virtual ground provided by a pair of 1K5 resistors across a 20V supply, as opposed to dual supplies of 10V
#1 Vp= -1.20V, Vgs @2mA = -335mV, Vgs @ 5mA = 106mV
#2 vp= -1.05V, Vgs @2mA = -294mV, Vgs @ 5mA = 158mV
#3 Vp= -1.55V, Vgs @2mA = -398mV, Vgs @ 5mA = 42.7mV
First time I've done this, so if there's any glaring errors, please mention it... other than the fact that as I understand it these aren't sj74's as I understand how to interpret the results.
So, my question to you all - what are they? And can I actually still use them in a mini AJ?
Addendum - I have a pile of J174's headed my way as a potential substitute... pending my learning to use them in that particular circuit!