On 9/6/2011 9:38 AM, Bob Blick wrote:
> Hi Matt,
>
> Attached is a circuit that I have used many times. This one is for eight
> inputs and protects against positive swings. It will work for +5 or
> lower, just attach the diode anode to the same supply as the micro.
>
> Cheerful regards,
>
> Bob
>
>
>
>
I like your idea, Bob.

It might be slightly improved by using 9 transistors instead of 8 plus=20
the diode in order to better match the Vbe.  And if possible, a=20
transistor array would probably have very close Vbe matching.  None of=20
this usually matters though.
--=20
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