On Tue, 23 Feb 1999 20:13:13 -0500 Sean Breheny <shb7@CORNELL.EDU>
writes:

>I ESPECIALLY don't understand why the positioning of the resistor
>along the
>line between the gate and the PIC would matter when it came to
>protecting
>the FET.

The resistor spoils the RF gain of the FET.  Unless part of a carefully
designed RF amplifier, RF gain is undesirable because it often leads to
oscillation.  If the FET oscillates, it will heat up and may burn out.

It doesn't matter what chip is driving the FET.  Generally the lower the
impedance of the driver's output, the worse the problem becomes.

The resistor needs to be installed near the FET because a long lead
attached to the gate will have some capacitance to ground and the rest of
the circuit.  The capacitance can couple RF to the FET and cause it to
oscillate.

___________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
or call Juno at (800) 654-JUNO [654-5866]