PicDude wrote:

> I need to switch on/off a 12V load, high-side, from a PIC running on 5V, and
> tried this circuit, but the output is always on.  With the PIC I/O floating
> (set as input), the load should be switched off, and with the I/O low, the
> load should be switched on.  I'm using 1k for R1 and 10K for R2.  The load
> will be up to ~250mA, btw.

Internal protection diodes of PIC's pins will make your transistor 
conduct all the time - since they shunt to 5.3Vcc (VDD+0.3 or so).

You should use a true Open Collector pin. Or place an intermediate 
transistor in between.

-- 
Ciao, Dario
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist