Message-ID: <001b01c27e0d$ee1c4560$0700000a@parissn2>
From: "Stewart Nelson" <sn@scgroup.com>
To: rsgb_lf_group@blacksheep.org
References: <001901c27e08$642b6980$e9847ad5@main>
Date: Mon, 28 Oct 2002 00:09:40 +0100
MIME-Version: 1.0
Subject: LF: Re: testing FETs
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Hi Peter and all,

Although a FET normally "blows" shorted, if the circuit
that it is in permits a huge current to then flow,
the internal bonding wire will act as a fuse and the
final result is an open.

With gate connected to source, measuring from source
to drain you should see a diode (N-channel part will
conduct when drain is negative).  From gate to source
there should be an open circuit with either polarity
(at normal ohmmeter voltages).  If both of these tests
pass, the device is probably ok, because any abuse
sufficient to blow the gate open would not leave the
drain to source circuit intact.

But, if you want to actually operate the device with
just an ohmmeter...

With gate open and measuring ohms from drain to source
(drain positive), the static charge from e.g. a comb
waved a couple of inches from the gate lead should turn
the device on and off.  Don't actually touch the gate
with the charged object; the ESD might damage it,
although high power devices are generally quite rugged.

73,

Stewart KK7KA