Pnp High Side Switch Circuit

Now this is the same circuit but the gate is connected to ground instead of 5 volts.

Pnp high side switch circuit. Figure 8 2 shows a circuit using a pnp transistor as a high side switch. The opposite of the low side switch is the high side switch. 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. Microcontroller interfacing part 12.

Part 8 showed how to use a pnp transistor allowing the load to be at ground potential as is sometimes necessary. The source is also at 5 volts. Similar to the npn circuit the base is our input and the emitter is tied to a constant voltage. The real switch is still the pnp transistor on the right.

Which means that pnp transistor shown in the first image will always be on regardless of the i o pin state. That means the vgs is 5v 5v 0v. Look at the voltages in this high side switch configuration. 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.

Therefore the circuit acts as open circuit and the led becomes off. The arrow in the emitter of a pnp transistor points in the opposite direction than in an npn transistor. This transistor connects between v and the load. When the switch at the base terminal is open no current flows through the base so the transistor is in the cutoff state.

Notice that the emitter is connected to the positive voltage. Just use an integrated high side switch something like auri3313 and a sot323 transistor and you have a high side switch with 10mohm 20a thermal protection short circuit protection for few. Typically these use a pnp bjt or p channel mosfet. This voltage means the mosfet is turned off or an open.

The gate is now at 5 volts. As discussed earlier that the transistor can be used as a switch. Here we are using electron flow from negative to positive this is often known as a series pass configuration. So the vgs in this case is 0 volts.

One limitation with the circuit described in. Using pnp transistors is essentially the same as npn transistors except the polarities are reversed. The schematic below shows how a transistor is used to switch the light emitting diode led. The circuit above is called a low side switch because the switch our transistor is on the low ground side of the circuit.

Using pnp transistors to switch higher voltage loads. We ll need a more complex circuit to implement a practical high side power on switch.