Experiments in Analog Electronics

150 Pages·2013·5.65 MB·English

Ministry of Higher Education and
Scientific Research
University of Technology
Department of Electrical Engineering
Analog Electronics Laboratory
Experiments in Analog
Electronics
By
Firas Mohammed Ali
2013
Ministry of Higher Education and Scientific Research
University of Technology
Department of Electrical Engineering
Analog Electronics Laboratory

Experiments in Analog
Electronics

By

Firas Mohammed Ali

Reviewed by

Nidhal H. Fathalla

&

Dr. Ahmed S. Ezzulddin

2013
Preface

Experiments in Analog Electronics is a manual designed specifically to enhance the practical
side of a contemporary course in analog electronic circuits for the second-year electrical
engineering students. Each experiment contains the necessary theoretical analysis of the
relevant topic beside the application circuits. A well-organized systematic procedure is also
included in each experiment to facilitate the practical work. In addition to that, discussion
questions and problems are added for the sake of extending student understanding of the
topic, and to increase his/her intuitive sense and thinking.

The practical circuits are to be implemented on breadboards using the off-the-shelf
components available in the laboratory, and then would be tested using suitable equipments
and instruments to see the operating characteristics of the circuit. Students can then compare
their measured quantities with the calculated values and write their reports. Students should
learn the construction of the practical circuits as well as the diagnosis of connection faults.
Their experience can be accumulated from one experiment to another.

In summary, this work is the outcome of two years teaching and training students the art of
practical electronic circuit implementation and testing. I hope that this effort be helpful and
adequate for the curriculum of second year electrical engineering.

Firas M. Ali
Baghdad, 2013

i
Acknowledgements

I would like to express my deep gratitude to the senior lecturer, Mrs. Nidhal H. Fathalla,
for reviewing the manuscript of this manual. Her valuable notes and suggestions were very
useful in writing the theoretical sections of the experiments. Actually, she has a long
experience in this field.

The continuous advice and technical support of Dr. Ahmed Saadoon Ezzulddin is highly
appreciated. His discussion and scientific notations about the topics, material, and procedures
of the experiments were very helpful in preparing them. He also provided me with a valuable
textbook about the subject.

Finally, I am also indebted to Assistant Prof. Dr. Hadi Tarish, the head of electronic
engineering division, for his encouragement and support.

ii
Table of Contents

Subject Page

Experiment 1: Diode Characteristics ……………………………………………….... 1
Experiment 2: Rectifier Circuits ……………………………………………………... 7
Experiment 3: Clipping and Clamping Circuits ……………………………………… 17
Experiment 4: The Zener Diode ……………………………………………………… 25
Experiment 5: Light Emitting Diodes ………………………………………………... 35
Experiment 6: Characteristics of Bipolar Junction Transistors ………………………. 41
Experiment 7: Transistor DC Biasing Circuits ………………………………………. 53
Experiment 8: Logic Gate Circuits …………………………………………………... 61
Experiment 9: The Common Emitter Amplifier ……………………………………... 73
Experiment 10: The Common Base Amplifier ………………………………………. 83
Experiment 11: The Emitter Follower ……………………………………………….. 89
Experiment 12: Amplifier Frequency Response …………………………………….. 95
Experiment 13: JFET Characteristics ………………………………………………... 101
Experiment 14: The Common Source Amplifier …………………………………….. 107
Appendix-A: Resistor Color Code Chart …………………………………………….. 113
Appendix-B: Data Sheets for Active Components …………………………………... 115

iii
Experiment 1 Diode Characteristics

Experiment 1

Diode Characteristics

Objectives

The purpose of this experiment is to measure and plot the forward and reverse IV
characteristics of a silicon diode, and to measure the DC and AC (dynamic) resistances of the
diode.

Required Parts and Equipments

1- DC Power Supply
2- Digital Multimeters
3- Electronic Test Board
4- Small Signal Silicon Diode 1N4148
5- Resistors, 470 Ω, 1 MΩ
6- Leads and wires

1. Theory

When a P-type and N-type semiconductor materials are effectively made on the same crystal
base, a diode is formed. The P-type side of the diode is called the anode, and the N-type side
is called the cathode. When the diode’s anode is at a higher potential than the cathode, the
diode is forward-biased, and current will flow through the diode from anode to cathode. On
the other hand, if the anode is at a lower potential than the cathode, the diode is said to be
reverse-biased, and only a very small reverse current flows from cathode to anode until break-
down occurs at a very high reverse voltage V , and a successive current may flow in the
BR
reverse direction. The breakdown voltage V is above 50V for typical diodes.
BR

Unlike a resistor, in which the current is directly (linearly) proportional to the voltage across
it, the diode is a nonlinear device. When the diode is forward-biased, a small voltage drop
occurs across it. This voltage drop is called the barrier potential with an approximate value of
0.3V for germanium diodes, and 0.7V for silicon diodes.

Fig.1 presents the IV characteristics curve for a typical semiconductor diode. This
characteristic curve can be approximately estimated in the forward-bias region from the
equation:

I = I (eVD/VT −1) (1)
D S

Where:

I : is the diode current
D
V : is the diode voltage
D
I : is the diode reverse saturation current
S
V : is the thermal voltage, which is approximately 26 mV at room temperature
T

- 1 -
Experiment 1 Diode Characteristics

Figure 1: Diode IV Characteristics

The diode forward static (or DC) resistance at a particular DC operating point (Q) is given by:

V
R = R = DQ (2)
DC D I
DQ

Where V is the diode bias voltage, and I is the diode operating current.
DQ DQ

The diode dynamic (or AC) resistance can be found from the characteristic curve at the Q-
Point as:

∆V
r =r = D (3)
ac d ∆I
D

Where ∆V is a small increment in diode voltage around V , and ∆I is a small increment in
D DQ D
diode current around I as depicted in Fig.2.
DQ .

The dynamic resistance depends on the operating point, and can be calculated approximately
from the equation:

V
r = T (4)
d I
DQ

Where V is the thermal voltage, and I is the diode operating current.
T DQ

Fig.2 shows the determination of the dynamic resistance graphically.

- 2 -
Experiment 1 Diode Characteristics

Figure 2: Graphical Determination of the Diode Dynamic Resistance

2. Procedure

1- Connect the diode circuit shown in Fig.3.

Figure 3: Diode Forward-Biased Circuit

2- Set the DC supply voltage V at 0V, and increase it gradually. Record diode voltage V and
in D
current I in each step according to Table 1 below.
D

Table 1: Recorded Data for the Forward-Biased Diode Circuit

ID (mA) VD (V)
0
0.5
1
2
4
6
8

10

12

16

18

20

22

- 3 -
Experiment 1 Diode Characteristics

3- Connect the reverse-biased diode circuit shown in Fig.4. Set the DC power supply voltage
V at 0V, and increase it gradually in several steps and record diode reverse voltage V and
in R
reverse current I as indicated in Table 2.
R

Figure 4: Diode Reverse-Biased Circuit

Table 2: Recorded Data for the Reverse-Biased Circuit

V (V) I (µA)
R R
0
5
10
15

20

25

3. Calculations and Discussion

1- Plot the diode forward characteristics from the results obtained, and determine the
cutin voltage V from the sketch.
γ

2- From the sketched characteristic curve determine the static resistance of the diode R
DC
at I = 10mA. Determine also the diode dynamic resistance at I = 10mA, and
DQ DQ
compare it with the theoretical value obtained from equation 4.

3- Plot the diode reverse characteristic, and estimate an approximate value for the reverse
saturation current I .
S

4- From the results obtained in this experiment, compute the maximum power dissipated
in the diode.

5- Explain how you could use an ohmmeter to identify the cathode of an unmarked
diode.

6- Explain why a series resistor is necessary when a diode is forward-biased.

- 4 -
Experiment 1 Diode Characteristics

7- In a certain silicon diode, it was found that the diode current is 15mA when the diode
voltage is 0.64V at room temperature. Determine the diode current when the voltage
across it becomes 0.68V. Use the approximate diode characteristic equation.

8- From the approximate diode characteristic equation, derive an expression for the
dynamic resistance r .
d

- 5 -