This time however the emitter is tied high.
Pnp transistor high side switch.
Which means that pnp transistor shown in the first image will always be on regardless of the i o pin state.
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.
Similar to the npn circuit the base is our input and the emitter is tied to a constant voltage.
The arrow in the emitter of a pnp transistor points in the opposite direction than in an npn transistor.
The first important thing to bear in mind to use a current limiting resistor at base.
Transistor name meaning lies in its own working.
The opposite of the low side switch is the high side switch.
Both npn and pnp transistors can be used as switches.
Npn transistor as a switch.
Transistor is 3 terminal electronic semiconductor component device.
Npn high side switch r2 works as a pullup resistor to keep the base positive when the npn is off so that the pnp is off too.
The circuit above is called a low side switch because the switch our transistor is on the low ground side of the circuit.
Higher base currents will damage a bjt.
Alternatively we can use a pnp transistor to create a high side switch.
Using pnp transistors is essentially the same as npn transistors except the polarities are reversed.
Transistor as switch.
To explain with a pspice model pn2907a transistor has been selected.
Because of how transistors work these can be a little more difficult to use in an arduino or raspberry pi circuit.
The real switch is still the pnp transistor on the right.
Notice that the emitter is connected to the positive voltage.
Typically these use a pnp bjt or p channel mosfet.
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.
The application of an pnp transistor is to work as a high side switch.
Figure 8 2 shows a circuit using a pnp transistor as a high side switch.
This transistor connects between v and the load.
A transistor has a 3 sandwich.
It has three terminals named as base emitter and collector.
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.
