level inverter 0v to 5v

[Timtoman]

I need a circuit that when lead "A" is grounded will allow a 3 to 5 volt output signal on lead "B".
When the ground on lead "A" is lifted lead "B" is now at or close to ground potential.
I have a 12 vdc power source and the current flow through lead "B" is minimal.

Thank You

 

[Exo]

Value for Pull-Up resistor R2 depends on your load... The less load the higher the resistor value may be...
The more load, the lower resistor value, but never drop below 150 ohm

As for the base resistor ... 10K will do

The voltage applied to R2 (12V on the scematic) is the voltage that will output when input is low...
So you should replace this 12V with a 5 - 3V supply