|
 The
Mosfet has the gate
insulated from the
substrate by a thin
layer of silicon oxide,
to prevent gate current
flowing and damaging the
device (see the page on
fets).
There are two main
families.
Enhancement - where the
Mosfet has to be forward
biased like a
transistor.
Depletion - where the
Mosfet is reverse biased
like a thermionic valve
(tube in the USA).
Some Mosfets have two
gates (dual gate Mosfets)
and are commonly used as
r.f. mixers.
The insulating layer is
extremely thin and can
be easily damaged by
static.
Antistatic precautions
must be taken when
handling them.
Soldering iron tips must
be earthed.
The operator must be
grounded via a high
value resistor, with
wrist straps etc.
The workplace must be
grounded safely.
Components must be
handled with care.
The operator should touch some
earthed point just
before handling static
sensitive devices.
Some devices have Zener
diodes built in, between
gate and source, for
protection. |
