Lesson 9:

Active Devices - Diodes, Transistors, and Tubes

Objectives:

When the students are finished this chapter they should be familiar with the basics of semiconductor devices and tubes. They should be able to name the parts of each and compare tubes and solid state devices.

Apparatus:

The circuit shown in figure 1, or its equivalent, is useful to demonstrate half-wave rectification. The transformer may be any low-voltage: 5 volts to 15 volts is suitable. A wall wart works fine here and has the advantage of safety. The circuit should be constructed on perfboard or other fairly solid support to prevent shorting. If clip-leads are used, then be sure the transformer does not become shorted.

Retain this circuit which will be used again in subsequent classes.

Handouts:

Block diagrams of diodes, NPN and PNP transistors, N-channel and P- channel FET's and triode. Printable copies of the handouts.

Lesson Plan:

In covering this chapter you do not have to have a PhD in solid state physics as you might infer from the Chapter 9 Quiz questions. Let the students read the text but in your classes focus mainly on the points that they will need to know to pass the exam.

fig 1: Experimental setup to demonstrate diode
and halfwave rectification

  1. Go over the homework from Chapter 8

  2. Pass around diodes. Show students how to identify the anode and cathode. Use an oscilloscope and circuit of figure 1 to demonstrate how a diode will permit AC to flow in one direction but is blocked in the opposite direction.

  3. Pass around different types of bipolar transistors. Have them identify the base, emitter, and collector. Use the diagrams to drill them on this.

  4. Pass around different types of FET's. Be careful to use only JFET's; MOSFET's will be damaged by static. Have the students identify the source, drain and gate. Use the diagrams to drill them on this.

  5. Set up a simple transistor amplifier circuit. Use an a voltmeter and an oscilloscope to show the following:
  6. Pass around samples of different IC's

  7. Pass around samples of different tubes, especially triodes. Try to obtain tubes that are large enough to see the various parts. Sacrifice a triode, tetrode, and pentode to higher education by carefully breaking the glass envelope so that each part of the respective tube is intact.

fig 2: Experimental setup to demonstrate basic
transistor operation

Homework:

  1. Read Chapter 9

  2. Do Chapter 9 Quiz

  3. Skim Chapter 10

Chapter 9 Quiz:

Printable copy of the Review Quiz

Answers to Chapter 9 Quiz
1 D 12 B 23 D 34 A 45 A
2 C 13 D 24 A 35 B 46 B
3 B 14 B 25 A 36 B 47 D
4 B 15 A 26 C 37 B 48 D
5 B 16 B 27 C 38 D 49 D
6 D 17 D 28 A 39 A 50 B
7 A 18 A 29 A 40 B 51 D
8 B 19 B 30 B 41 D * *
9 D 20 C 31 B 42 B * *
10 B 21 D 32 D 43 B * *
11 C 22 B 33 B 43 A * *

Overhead Slide Versions of the Diagrams

  1. Slide 1
    9.1 PN junction, forward biased
    9.2 PN junction, reverse biased
    9.3 Diode symbol and typical packages

  2. Slide 2
    9.4 Three layer semiconductor sandwich
    9.5 NPN and PNP circuit diagrams

  3. Slide 3
    9.6 NPN bias and current flow
    9.7 PNP bias and current flow

  4. Slide 4
    9.8 FET physical diagram
    9.9 p-FET and n-FET Circuit Diagrams

  5. Slide 5
    9.10 Gain diagram
    9.11 Basic NPN circuit
    9.12 FET Common Collector circuit

  6. Slide 6
    9.13 Tube, physical layout
    9.14 Diode Tube, circuit diagram

  7. Slide 7
    9.15 Triode Tube, circuit diagram
    9.16 Triode Tube, electrical connections

  8. Slide 8
    9.17 Schematic diagrams, tube, NPN transistor, FET

  9. Slide 9
    9.14 Diode Tube, schematic diagram
    9.15 Triode Tube, schematic diagram
    9.19 Tetrode Tube, schematic diagram
    9.20 Pentode Tube, schematic Diagram