Electronics

electronics fundamentals circuits, devices, and applications
THOMAS L. FLOYD
DAVID M. BUCHLA

Lesson 2: Transistors and Applications
Electronics Fundamentals 8th edition
Floyd/Buchla

© 2010 Pearson Education, Upper Saddle
River, NJ 07458. All Rights Reserved.

Lesson 2
Introduction
A transistor is a semiconductor device that controls current between two terminals based on the current or voltage at a third terminal.
It is used for amplification or switching of electrical signals.
The basic structure of the bipolar junction transistor, BJT, determines its operating characteristics.
DC bias is important to the operation of transistors in terms of setting up proper currents and voltages in a transistor circuit.
Two important parameters are αDC and βDC

Electronics Fundamentals 8th edition
Floyd/Buchla

© 2010 Pearson Education, Upper Saddle
River, NJ 07458. All Rights Reserved.

Lesson 2
Bipolar junction transistors (BJTs)

The BJT is a transistor with three regions and two pn junctions. The regions are named the emitter, the base, and the collector and each is connected to a lead.
There are two types of
BJTs – npn and pnp.

B (Base)

C (Collector)

n p n

Base-Collector junction B

Base-Emitter junction E (Emitter)
Electronics Fundamentals 8th edition
Floyd/Buchla

Separating the regions are two junctions. C

p n p

E
© 2010 Pearson Education, Upper Saddle
River, NJ 07458. All Rights Reserved.

Lesson 2
Bipolar junction transistors (BJTs)

FIGURE 17–2 Transistor symbols.
Electronics Fundamentals 8th edition
Floyd/Buchla

© 2010 Pearson Education, Upper Saddle
River, NJ 07458. All Rights Reserved.

Lesson 2
BJT biasing

For normal operation, the base-emitter junction is forwardbiased and the base collector junction is reverse-biased.

For the npn transistor, this pnp condition requires that the base is more positive than the emitter negative than the emitter collector is