MOSFET
The enhancement mode N-Channel MOSFET, where the switch between the "source" and "drain" is usually off. You can turn the switch on by applying a positive voltage to the "gate", so it is at a higher voltage than the "source". The P-Channel MOSFET is also usually off, but you use a negative voltage to turn it on. The Depletion mode N and P-Channel MOSFET transistors are very similar to their enhancement mode counterparts, but they are normally on, and you use a negative or positive voltage to turn it off. The Depletion mode P-Channel MOSFET isn't normally available for use.