WH Tan wrote:
>
> > One PNP transistor, (high side) and 3 resistors.
> > Connect the resistors as a 3 section voltage
> > divider
>
> Thanks for your reply.
> But I can't understand what you means '3 section voltage divider'. Could you
> please point me how to connect the resistors.


OK. :o)
Here it is, the resistor divider is set so that;

digital pin=5v,  B-E voltage=0.5v,   PNP=OFF
digital pin=0v,  B-E voltage=0.83v,  PNP=ON

It has a couple of minor drawbacks, it wastes some
current through the 3R divider even when the PNP
is off, and if you need to switch significant current
you need to lower all the resistor values or maybe
use a darlington PNP.

But for a very simple low power solution (like a
way to switch programming Vpp 13v) it works fine
and saves one transistor.
:o)
-Roman


+13v -------------------------------*---------*----
                                    |         |
                             0.5v   R1        |
                          560 ohm   |         E
                                    *-------B     PNP
                                    |         C
                                    |         |
                                    R2        |
 digital signal               8k2   | 7.6v    '----  switched
 (or PIC ouput pin)                 |                13v out
                                    |
        *---------------------------*
   (0v or 5v signal)                |
                                    |
                              5k6   R3
                                    | 5v
                                    |
gnd  -------------------------------*--------------

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