Yes, it is a diode connected mosfet.

TAS

At 10:03 AM 11/9/99 +1000, you wrote:
>On Mon, 08 Nov 1999, you wrote:
>> Hello List,
>>
>> I have realized an alarm for my bycicle using a 12C508. It is powered by
two AA
>> size alkaline battery.
>>
>> I would like to know if there is a simple (and economic!!) solution which
>> I can use to protect my circuit against polarity inversion during
battery change.
>> (I know it's a remote possibility, but it exists)
>>
>> I thought to use a serie diode, but the voltage drop bring the PIC power
voltage
>> near the power supply limit of the MCU.
>>
>I can't think of it right now, but there is an arrangement using a single
>MOSFET which will provide this. Possibly the gate is connected to the drain,
>possibly it is an N-channel MOSFET, and possibly the circuit is in
Horowitz and
>Hill. It's a very simple circuit, but as I said, I can't think of it now
(such
>is the effect of a few beers..). Play around with this, and see what you can
>come up with. I'll try again in the morning.
>
>Jason Langenauer
>Mechanical and Space Enginnering, The University of Queensland
>--
>Lady Astor: If you were my husband, I'd poison you drink.
>Winston Churchill : If I was your husband, I'd drink it.
>
>
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