Re: gEDA-user: PCB footprints

[phil@xxxxxxxxxxxxxxxxxxxxxxxx]

Dan McMahill <dan@xxxxxxxxxxxx> wrote:
> 
> Out of curiosity, have you ever come across any sort of textbook 
> treatment of dual-gate FETs?  

Art of Electronics has a small reference to dual gate fets Chapter 13.11
"tuned amplifiers" (pg. 883).  

Their description is somewhat opaque, but one gate biases the device and
serves as the input (it's grounded thru an R so it's biased to Idss).  The
other gate is just a shield because it is 'biased' way higher than the other
gate so therefore doesn't aid in channel conduction, but does get grounded
thru a large cap.  It's is a capacitive shield between the drain and the
signal gate because of the way the part is made, like a tetrode in this
regard.  How to design the bias voltage on the extra gate, I'll leave to
Karel.

Phil Taylor