I get it now. Thank you very much.

For those who have reply suggesting a darlington TR, I really appreciate
your time. Roman is right, darlington TR is unnecessary since I am using it
for turning on a Vpp supply to a PIC.


WH Tan


> 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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>
>

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