8-pin DIP pinout for JFET?

[Bearded Occam]

I have a schematic showing a part identified as J412, which is
probably a National Semiconductor NJFET. The schematic only shows the
pin numbers, not the JFET symbol itself, so I can't guess the pinout.
I suspect there might at one time have been a generic 8-pin DIP pinout
for JFETs, but I can't confirm this. Or I could be wrong about what a
J412 is. Of all things, it's part of an ancient solid state guitar amp.

 

[Ecnerwal]

In article
<36ef6454-49ed-410c-a0fe-33648689baf1@n20g2000hsh.googlegroups.com>,
Bearded Occam <BeardedOccam@gmail.com> wrote:

I have a schematic showing a part identified as J412, which is
probably a National Semiconductor NJFET. The schematic only shows the
pin numbers, not the JFET symbol itself, so I can't guess the pinout.
I suspect there might at one time have been a generic 8-pin DIP pinout
for JFETs, but I can't confirm this. Or I could be wrong about what a
J412 is. Of all things, it's part of an ancient solid state guitar amp.

There was an LF412 dual jfet op-amp -

1 out a v+ 8
2 - in a out b 7
3 in a -in b 6
4 v- in b 5

I don't have any J412 in my databooks, and the J parts I do have are
TO92/SOT-23 FETS. There is a dual FET in 8 pin layout for a completely
different series of FETs, but see if it makes any sense with your
schematic (the NC's might help):

S G
D NC
NC D
G S

Note the package can be put in backwards and still work.

--
Cats, coffee, chocolate...vices to live by

 

[Mark Zenier]

In article <36ef6454-49ed-410c-a0fe-33648689baf1@n20g2000hsh.googlegroups.com>,
Bearded Occam <BeardedOccam@gmail.com> wrote:

I have a schematic showing a part identified as J412, which is
probably a National Semiconductor NJFET. The schematic only shows the
pin numbers, not the JFET symbol itself, so I can't guess the pinout.
I suspect there might at one time have been a generic 8-pin DIP pinout
for JFETs, but I can't confirm this. Or I could be wrong about what a
J412 is. Of all things, it's part of an ancient solid state guitar amp.

I'm pretty sure that that's an old Siliconix number. But the Siliconix
discrete book that I have doesn't have the datasheet, or the datasheet for
the part that's given as equivalent, U412. (Usually J parts are plastic,
and U parts with the same number are the same thing in TO5 or some other
metal can).

Looking in an old GE Intersil book, they don't have the J412 either,
but do say that the IT502 is an equivalent. But they say the U412
is equivalent to the 2N3958.

Now it gets confusing. The IT502 is a dual cascode amp (2 sets of
cascode amps each with 2 JFETS), while the 2N3958 is just a dual JFET.

One place to look is Vishay, as they took on the Siliconix discrete
parts lines.

(I also vaguely remember somebody posting about the J412 for an
oscilliscope repair, a year or three back).

Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)