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How does a PNP transistor work?

how does a pnp transistor work

This is as simple an explanation of how does a PNP transistor work as I could get it. You can go into pages and pages of complex theory and get lost and not understand. That’s what happened to me when I tried to learn. You can get whole books written on how transistors work and I would suggest that if that’s what you want you can get one. This is just for pure beginners.

A transistor is a three legged electronic component that is operated by an electrical current. A PNP transistor is one type of bipolar junction transistor or BJT as they are sometimes known. The other being the more common NPN transistor. For instructions on how they work read here.

The three legs are connections for.

1. The base

2. The collector

3. The emitter

This is the symbol for a PNP transistor.

how does a pnp transistor work symbol

In the circuit below the PNP transistor is “off”.

how does a pnp transistor work circuit

To turn it on connect the open end of R1 to ground.

PNP transistors are not surprisingly opposite polarities to NPN transistors. An important thing to remember that used to confuse me is.

NPN transistors “source” current through the base.

PNP transistors “sink current into the base.

If you are familiar with the operation of a NPN transistor a small current flows, base to emitter, causing a larger current to flow, collector to emitter.

With a PNP not only is the polarity reversed but also the current flow so a small current flows, emitter to base, causing a larger current to flow, emitter to collector.

If you want to test a PNP transistor with a multimeter with a diode range you can read how to do it here, however I can thoroughly recommend this device from Amazon DEOK Multifunction Transistor Tester Mega328 NPN/PNP Transistor Checker Capacitor ESR SCR/MOSFET/Resistor/Diodes Meter LCD Display (Small). Not only will it test transistors you don’t need to know what they are or the lead configuration. You just connect its three legs to connections 1, 2 and 3 and press the test button. It will then tell you which legs are the base, collector and emitter and whether the device is a working NPN or PNP transistor. You can read more about the transistor tester here.

If you want to experiment with transistors read here for which NPN and PNP common transistors are available.

If you want to know how a NPN transistor works read here.