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:
- Diodes of various types and power ratings
(single, bridge,
Zener, LED)
- transistors and FET's of various types and power ratings
- samples of IC's
- VOM, oscilloscope, AC power transformer and resistor
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
- Go over the homework from Chapter 8
- 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.
- Pass around different types of bipolar transistors. Have them
identify the base, emitter, and collector. Use the diagrams to drill
them on this.
- 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.
- Set up a simple transistor amplifier circuit. Use an a
voltmeter and an oscilloscope to show the following:
- when the voltage on the base goes more positive (pot toward the
positive battery terminal), the collector voltage becomes more
negative
- there are two saturaton points at which no amount of adjustment of
the pot will increase (or decrease) the collector voltage
- use the AC signal from previous experiment (through a small
capacitor to the base) to show amplification
- show that excessive input or badly adjusted bias will cause severe
waveform distortion
- Pass around samples of different IC's
- 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:
- Read Chapter 9
- Do Chapter 9 Quiz
- 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
- Slide 1
9.1 PN
junction, forward biased
9.2 PN junction, reverse biased
9.3 Diode
symbol and typical packages
- Slide 2
9.4
Three layer semiconductor sandwich
9.5 NPN and PNP circuit
diagrams
- Slide 3
9.6 NPN bias and current flow
9.7 PNP bias and current
flow
- Slide 4
9.8
FET physical diagram
9.9 p-FET and n-FET Circuit Diagrams
- Slide 5
9.10
Gain diagram
9.11 Basic NPN circuit
9.12 FET Common Collector
circuit
- Slide 6
9.13
Tube, physical layout
9.14 Diode Tube, circuit diagram
- Slide 7
9.15
Triode Tube, circuit diagram
9.16 Triode Tube, electrical
connections
- Slide 8
9.17
Schematic diagrams, tube, NPN transistor, FET
- 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