Experiment 6 - The PNP Transistor II

Here the PNP transistor switches through. Note the difference to the NPN transistor.

Consider the circuit shown. The PNP transistor switches through, when the base is connected to the negative terminal of the battery (0 V). When you press the pushbutton switch, the light-emitting diode LED1 lights up. Circuit with PNP transistor. (Enlarge) Now a small current IB flows out of the PNP transistor through the base. The illustration shows the different currents.

Circuit diagram with PNP transistor.

PNP Transistor When a small current flows from the collector and out of the base, the PNP transistor switches. As a result, a much larger current flows from the collector to the emitter.

Currents through a switched through PNP transistor.

PNP transistors are far less common than NPN transistors. Due to their internal layout, PNP transistors are usually slower and conduct less current. You find information on why this is so, in the topic "Transistor" in the section semiconductor physics.

In the following experiments you take a look at the most common applications of transistors, switches and amplifiers.