Luxman R-5045 - Needing help identifying component in AM/FM module

[mikkele86]

hello.

I came across this thing and im not sure what it is exactly, I have never seen such thing before.
I know it gotta be some kind of diode with Drain, Source and Gate1 and gate2

It resides in AM/FM module and im measuring 200ohm across D and S.

[mikkele86]

and the back look ilke this

[CapLeaker]

It's an old school JFET used to amplify weak signals in the receiver

[eccerr0r]

Before all the rage of MOSFETs being used as switches, they were used as class C signal amplifiers, and this is a dual gate MOSFET.

[mikkele86]

ahh okay. many thanks

[CapLeaker]

Google “dual gate jfet” or look at a BF981

[CapLeaker]

Actually this particular device is a GasFet 2SK85.

[eccerr0r]

Eh... GaAs is fairly "recent" ... Is that a dual source or dual gate MOSFET? Depletion or enhancement?