Pnp High Side Switch Circuit

Which means that pnp transistor shown in the first image will always be on regardless of the i o pin state.

Pnp high side switch circuit.

As discussed earlier that the transistor can be used as a switch. So the vgs in this case is 0 volts. Referring to plate 1 whenever the voltage difference between the gate g and source s exceeds around 5 volts this opens a conductive channel between source s and drain d allowing current flow from the source back to the power supply. Using pnp transistors to switch higher voltage loads.

Microcontroller interfacing part 12. Similar to the npn circuit the base is our input and the emitter is tied to a constant voltage. This transistor connects between v and the load. We ll need a more complex circuit to implement a practical high side power on switch.

When the switch at the base terminal is open no current flows through the base so the transistor is in the cutoff state. Figure 8 2 shows a circuit using a pnp transistor as a high side switch. Because of how transistors work these can be a little more difficult to use in an arduino or raspberry pi circuit. The schematic below shows how a transistor is used to switch the light emitting diode led.

Now this is the same circuit but the gate is connected to ground instead of 5 volts. The easiest way to switch a higher power load than a microcontroller can handle is to use an npn transistor as explained in part 7. Using pnp transistors is essentially the same as npn transistors except the polarities are reversed. Typically these use a pnp bjt or p channel mosfet.

One limitation with the circuit described in. The circuit above is called a low side switch because the switch our transistor is on the low ground side of the circuit. This voltage means the mosfet is turned off or an open. The real switch is still the pnp transistor on the right.

The arrow in the emitter of a pnp transistor points in the opposite direction than in an npn transistor. Here we are using electron flow from negative to positive this is often known as a series pass configuration. The opposite of the low side switch is the high side switch. The gate is now at 5 volts.

Part 8 showed how to use a pnp transistor allowing the load to be at ground potential as is sometimes necessary. Look at the voltages in this high side switch configuration. The source is also at 5 volts. That means the vgs is 5v 5v 0v.

Therefore the circuit acts as open circuit and the led becomes off. This time however the emitter is tied high.