High Side Switch Transistor. You can also switch the high side with a PNP transistor and have the base resistor to ground. This requires both a robust low on-resistance power switch and accurate analog circuitry for diagnostic protection and control functions.
For example short circuit protection can protect the MOSFET if a short to groundbattery occurs. Is it acceptable for. Since the switching element the transistor was at ground it is called a low side switch With low side switching the load is at Vcc potential.
In a P-channel device the conventional flow of drain current is in the negative direction so a negative gate-source voltage is applied to switch the transistor ON.
A TIP32C is pretty cheap and sold by Jameco for 39 cents shipping or go onto ebay for still cheaper sources. In a P-channel device the conventional flow of drain current is in the negative direction so a negative gate-source voltage is applied to switch the transistor ON. The N Channel High Side Switch The main problem in using an N channel MOSFET in a high side switch is that in order for the MOSFET to switch on once it has been switched off is that the voltage on the gate terminal of the MOSFET must be made higher than the source voltage which as the MOSFET is off will be at supply voltage Vcc. For example short circuit protection can protect the MOSFET if a short to groundbattery occurs.