Semiconductor Fundamentals Unit 5 – Transistor Junctions & PNP DC Bias
UNIT 5 – TRANSISTOR JUNCTIONS & PNP DC BIAS
UNIT OBJECTIVE
At the completion of this unit, you will be able to test transistors and demonstrate a transistor
switch by using PNP and NPN transistor circuits.
UNIT FUNDAMENTALS
When another section of P or N type material is added to a PN diode junction, a three-section
device containing two junctions is formed. This three-section semiconductor device is a bipolar
transistor. The three sections are the emitter (E) and collector (C) on the ends and the base (B) in
the middle.
Transistors are classified by the arrangement of the P (positive) and N (negative) type materials.
Transistors are either PNP or NPN types, as shown. Each of the two PN junctions of a transistor
have forward and reverse voltage/current characteristics similar to a diode PN junction.
Q is the letter used to identify a transistor. The emitter arrows in the NPN and PNP transistor
symbols show the direction of conventional current flow. Electron current flow, which is in the
opposite direction of conventional current flow, is used in this course.