Because of how transistors work these can be a little more difficult to use in an arduino or raspberry pi circuit.
Pnp high side switch.
The gate is now at 5 volts.
Building a high side switch with 2 components.
The arrow in the emitter of a pnp transistor points in the opposite direction than in an npn transistor.
High side switches can safely drive high currents into complex resistive inductive and capacitive grounded loads in compliance with the harsh automotive environment.
This transistor connects between v and the load.
The opposite of the low side switch is the high side switch.
We ll need a more complex circuit to implement a practical high side power on switch.
Now this is the same circuit but the gate is connected to ground instead of 5 volts.
Which means that pnp transistor shown in the first image will always be on regardless of the i o pin state.
Notice that the emitter is connected to the positive voltage.
This requires both a robust low on resistance power switch and accurate analog circuitry for diagnostic protection and control functions.
Typically these use a pnp bjt or p channel mosfet.
The source is also at 5 volts.
Using pnp transistors is essentially the same as npn transistors except the polarities are reversed.
A p channel mosfet and a resistor.
That means the vgs is 5v 5v 0v.
Figure 8 2 shows a circuit using a pnp transistor as a high side switch.
The real switch is still the pnp transistor on the right.
So the vgs in this case is 0 volts.