I have a 0/5v square wave and I need to level shift it, I can easily use a pnp transistor and shift it to a 0/12v wave. However I would like to use the same transistor to level shifted the 0/5v wave to -12/0 and no matter which way around I put the setup I cant seen to get it to work. Cant this be done ?. The load on the -12 supply will only be around 1.2ma.

 

This probably can be done, but more information would help. For instance, how do the input and output correspond?

5V in to give 0V out suggests common base, but perhaps you want 5V in for -12V out?

How much current can the original 5V signal source deliver? Have you got a -12V supply?