Field Effect Pentode Transistor?

[Jered]

  Does anybody know anything about these? I wonder if they will work for small signal audio?
http://www.freepatentsonline.com/4104673.html

[Steben]

something like this?

or this?

The dual gate FET is compared to multi-grid tubes, so I guess it is something like this.

[Sir H C]

Not good for audio.  Those are devices made to run at 20 GHz in a GaAs process.  Similar to cascoding but with that fifth terminal.  The patent is from the late 70s and I have not ever seen one in use, so I would assume it was a dead end. 

[Jered]

Not good for audio.  Those are devices made to run at 20 GHz in a GaAs process.  Similar to cascoding but with that fifth terminal.  The patent is from the late 70s and I have not ever seen one in use, so I would assume it was a dead end. 

  That was exactly what I was wondering. I've never seen them either. Thank you Sir.

[DDD]

As far as I know there is JFET tetrode exists. It's a low power small signal JFET with two SEPARATE gates designed in the USSR and still produced in Russia. Its mark is "ÊÏ304" if I remember truly.

[Sir H C]

Dual gate devices are here too.  Usually for high frequency RF where the second gate acts like a cascode device to lower the parasitic capacitance from input to output (to reduce tendency to oscillate and to raise the input impedance).  Where I used to work, one of the research guys was really into his dual-gate devices.  It got to where we would parody his way of saying duuualll gate.