Can someone please explain the voodoo of the transistor as a switch. I have a TIP122 Darlington pair transistor that I am trying to use to apply 9V to a load when I apply 5V to the base. I currently have it so that 9V is connected to the Collector, middle pin. The emitter is connected to the + side of an LED. This then goes thru a resistor to ground. I have a 5v switched power supply connected with the + lead connected to the base and the - lead connected to ground. This is on a project board so the ground rail for the 9V power and the 5V power are the same. When I turn on the 5v power supply, the LED lights up but there are only 5V going thru it. What happened to the 9V?