Mark Willis wrote:
>>
>> See an-ecd02.zip at:
>>
>> http://www.users.uswest.net/~oricom/appnote.htm
>>
>
>This URL redirects to http://www.users.qwest.net/~oricom/appnote.htm
>which 404's from here.  I think I'm using the exact same circuit and
>mentioned part of it (2 diodes to the PC's serial output, one to the
>cap, the other is on the other side of a resistor and prevents an NPN
>transistor's base from being pulled below -0.7V, etc.)  It's a pretty
>good solution really, all in all.  I've seen MOSFET implementations of
>this, and ones with NPN and PNP transistors, prefer the PNP / NPN
>implementations as they're cheaper for production <G>
>

Oops, sorry, try:

http://www.users.uswest.net/~oricom/appnotes.htm


Mark, you are correct that including a diode from the base of the
Rx tansistor to gnd [anode to gnd] is helpful in preventing E-B
reverse breakdown. I typically now use a 2:1 voltage divider in
the base to prevent this. 10K Rx-to-base, 4.7K base-to-gnd.
Guess I should update the appnote.

- Dan Michaels
Oricom Technologies
===================

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