Similar to the npn circuit the base is our input and the emitter is tied to a constant voltage.
Pnp transistor high side switch.
I saw a suggestion on using a pnp for switching a load on the low side with the collector grounded emitter following the input first diagram as opposed to the high side.
To explain with a pspice model pn2907a transistor has been selected.
The real switch is still the pnp transistor on the right.
Trans istor transistor the prefix trans tells about signal transfer from low resistance to high resistance part and istor means solid physical structure having property of resistance.
Transistor name meaning lies in its own working.
Using pnp transistors is essentially the same as npn transistors except the polarities are reversed.
Some of the applications use a power transistor as switching device at that time it may necessary to use another signal level transistor to drive the high power transistor.
We ll need a more complex circuit to implement a practical high side power on switch.
Because of how transistors work these can be a little more difficult to use in an arduino or raspberry pi circuit.
Alternatively we can use a pnp transistor to create a high side switch.
Transistor as switch.
Transistor is 3 terminal electronic semiconductor component device.
Npn transistor as a switch.
The arrow in the emitter of a pnp transistor points in the opposite direction than in an npn transistor.
The application of an pnp transistor is to work as a high side switch.
I normally would switch the high side second diagram but i guess the first method should also work although it would dissipate more power in the transistor and not have.
It has three terminals named as base emitter and collector.
Higher base currents will damage a bjt.
Notice that the emitter is connected to the positive voltage.
The opposite of the low side switch is the high side switch.
A transistor has a 3 sandwich.
When npn turns on it sinks current through r1 r2 and this creates a voltage drop to the base of pnp which turns it on.
This time however the emitter is tied high.
The first important thing to bear in mind to use a current limiting resistor at base.
Figure 8 2 shows a circuit using a pnp transistor as a high side switch.
Based on the voltage applied at the base terminal of a transistor switching operation is.
Which means that pnp transistor shown in the first image will always be on regardless of the i o pin state.
This transistor connects between v and the load.
The circuit above is called a low side switch because the switch our transistor is on the low ground side of the circuit.
