Basic electronic, Exercises of Basic Electronics

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BASIC ELECTRONICS

LAB MANUAL

TABLE OF CONTENTS

LAB 01: Introduction to Basic Electronics Lab & Equipment Survey.

LAB 02: Testing Diodes.

LAB 03: V-I Characteristics Diode.

LAB 04: Half-wave Rectifier.

LAB 05: Full-wave Bridge Rectifier.

LAB 06: Full-wave Rectifier Using Center Tapped Transformer.

LAB 07: Zener Diode and Voltage Regulation.

LAB 08: Clipper Circuits.

LAB 09: Clamper Circuits.

LAB 10: Testing Transistors.

LAB 11: Transistor Base Biasing and Load Line.

LAB 12: Transistor as a Switch.

LAB 13: Transistor Emitter Biasing.

LAB 14: Common Emitter Amplifier.

LAB 15: Common Base Amplifier.

LAB 16: Common Collector Amplifier.

4. Select the required range. The digital multimeter needs on and the required range selected.

The range selected should be such that the best reading can be obtained. Normally the multimeter function switch will be labeled with the maximum resistance reading. Choose the one where the estimated value of resistance will be under but close to the maximum of the range. In this way the most accurate resistance measurement can be made.

5. Make the measurement. With the multimeter ready to make the measurement the probes can be applied to the item that needs to be measured. The range can be adjusted if necessary.
6. Turn off the multimeter. Once the resistance measurement has been made, the multimeter can

be turned off to preserve the batteries. It is also wise to turn the function switch to a high voltage range. In this way if the multimeter is used to again for another type of reading then no damage will be caused if it is inadvertently used without selecting the correct range and function.

7. Digital millimeters are ideal pieces of test equipment for measuring resistance. They are relatively cheap and they offer a high level of accuracy and general performance.

Precautions:

1. Measure resistance when components are not connected in a circuit:
2. Remember to ensure the circuit under test is not powered on
3. Ensure capacitors in a circuit under test are discharged
4. Remember diodes in a circuit will cause different readings in either direction
5. Leakage path through fingers can alter readings in some cases.

Oscilloscope:

Theory:

In this lab, you’ll learn the basics of how to use an oscilloscope. Then you’ll investigate time Dependent circuits. These questions and lab activities are designed to help you develop an understanding of these circuits, allowing you to address conceptual questions without plugging through unnecessary math. You’ll also see what these circuit components look like in real life.

Procedure:

Reset the oscilloscope:

1. Turn on the oscilloscope, and disconnect any probes plugged into the “channel 1” (CH 1) input connector.
2. Set all the levers and buttons as indicated, if they’re not already.

3. Set the CH 1 coupling mode switch to “ground” (GND).
4. Turn down the INTENSITY knob, if necessary, to avoid burning out the screen.
5. The sweeping dot should be clear but not too bright.
6. Since channel 1 is now “grounded” to zero volts, the oscilloscope should read zero on the

vertical axis (using the coordinate axes centered on the screen).

7. Adjust the channel 1 vertical POSITION knob so that the oscilloscope reads 0 volts.

What the oscilloscope does:

1. The oscilloscope graphs voltage vs. time, by sweeping an electron beam across the phosphor screen.
2. Wherever the beam hits the screen, it glows green.
3. For most measurements, the beam sweeps rightward at a constant rate.
4. When the beam gets to the right-hand side of the screen, it jumps back to the left-hand side.

In this way, the horizontal axis shows time.

5. When a probe is plugged into the CH 1 input connector, the vertical axis shows the potential difference—i.e., the voltage—between the two wires coming out of that probe.

Measuring DC voltages, and using the VOLTS/DIV

setting:

1. The point of this brief activity is to practice measuring a voltage with the oscilloscope, and to

get a feel for what the VOLTS/DIV control does.

2. Set the CH 1 VOLTS/DIV to 2.
3. Set the CH 1 coupling mode switch to DC.
4. Now use the oscilloscope to measure the voltage across a 1.5-volt battery.
5. Make sure you understand what the VOLTS/DIV setting is doing. Students often err in thinking in terms of DIV/VOLT instead of VOLT/DIV.
6. To get a more precise reading of the battery’s voltage, should you turn the VOLTS/DIV knob

clockwise or counterclockwise? Why? Try it, to get a feel for how much precision can be gained.

Measuring AC voltages, and the Time/DIV setting:

1. Now you’ll practice using an AC power supply, and you’ll figure out what the SEC/DIV

knob does.

2. The “AC” means “Alternating Current”—that is, the voltage put out by the power supply oscillates with a frequency that you set.
3. (^) Set SEC/DIV to 0.5 milliseconds.

LAB 02

Testing Diode

Objectives:

1. To determine a practical method of testing semiconductor diodes.
2. To determine if the diodes in your parts pack are shorted or open.

Apparatus:

.1 Ohmmeter

.2 1-Germanium diode

.3 1-Silicon diode

.4 1-Zener diode

.5 2-LEDS

Theory:

Semiconductor diodes can be tested by a variety of methods. Oscilloscope curve tracers and specially constructed transistor testers can be used to determine the characteristics and the condition of a diode. However, in most cases diodes are tested primarily to see if they are simply shorted or open rather than to determine their detailed specifications. For that reason a simple go/no go test method is preferred in most situations. A quick and easy diode test can be made with most ohmmeters. This experiment describes the procedure and theory used when testing diodes with an ohmmeter.

Procedure:

1. Consider the 2 legs of the diode as leg 1 and leg 2
2. Place the knob o the multimeter on diode option and fill the following table

Red lead Black lead Voltage drop Leg1 Leg Leg2 Leg

3. When red lead is attached to the anode and black to the cathode a voltage drop of 0.7 will be observed. And infinite in the other case. If the above is coming than the diode is not short nor open.
4. Now note the following:

Rf Rr Rr/Rf Silicon diode Germanium diode

5. Reverse resistance is greater than the forward resistance. The higher the ratio the better the diode.

Discussion:

1. The diode consists of two parts:
2. The N material is called the cathode.
3. The P material is called the anode. Current flows from cathode to anode.
4. Bias determines whether a diode conducts or is cut off.
5. Forward bias allows a diode to conduct.
6. Reverse bias blocks conduction, or cuts off a diode.
7. With forward bias, current increases as the voltage increases.
8. With reverse bias, reverse current is minimal until avalanche conduction is reached.

3. Now wire the circuit as shown in fig 2. Adjust the dc power supply to give the voltages across the 1- K ohm resistor shown in table 1. For each voltage measure and record the dc voltage drop (V (^) d ) across the diode. The diode current is also the current flowing through the 1-K ohm resistor. Determine the diode current by using Ohm’s law in each case.

Fig 01

Table 1

Voltage across 1 K ohm resistor

Diode Voltage Diode Forward Current(10^-3)

0.1V 0.2V 0.3V 0.4V 0.5V 0.6V 0.7V 0.8V 0.9V 1V 2V 3V 4V 5V 6V 7V 8V 9V 10V Graph Data

LAB 04

Half Wave Rectification

Objectives:

1. To demonstrate the half wave rectification using a silicon diode

Background:

Simply defined, rectification is the conversion of alternating current (AC) to direct current (DC).

Rectification is a process whereby an applied waveform of zero average value is changed to one

that has a dc level. The process of removing one-half the input signal to establish a dc level is

called half-wave rectification. The dc level obtained form half-wave rectification can be improved 100% using a process called full-wave rectification.

Apparatus:

1. Multimeter
2. Trainer with AC Power Supply
3. Bread board
4. Connecting wires
5. Resistor 1KΩ
6. 1N4001 Silicon Diode
7. Oscilloscope

Formulae:

Half-wave rectifier

Output voltage (^) max (V (^) max ) =input voltage (^) max - V (^) T

Output frequency = input frequency

DC Voltage (VDC) =0.318 (Output voltage (^) max )

Procedure:

3. Bread board
4. Connecting wires
5. Resistor 1KΩ
6. Four1N4001 Silicon Diode
7. (^) Oscilloscope

Formulae:

Full-Wave rectifier

Output voltage (^) max (V^ max ) = input voltage^ max - 2V^ T

Output frequency = 2 x input frequency

DC Voltage (VDC) = 0.636 (Output voltage (^) max)

Procedure:

1. Wire the full-wave rectifier circuit as shown in figure as per your convenience. Pay special attention to the polarities of diodes.
2. If everything is connected properly, you should obtain the waveform shown in figure 3. With

your Multimeter measure the dc voltage. Use formulas provided above to figure out the difference between the peak voltage of input waveform and that of the output waveform. Notice that the frequency of the output waveform this time is the twice that of the input sine wave.

Figure 1. Full Wave Rectification Bridge Circuit

Figure 2. Input Signal Waveform

Figure 3. Full-wave rectification output waveform

Table 1:

Parameter Full-wave Rectifier V (^) s(max i/p voltage) V (^) max V (^) DC

LAB 06

Full Wave Rectification Using Center-taped Transformer

Objectives:

1. To demonstrate the characteristics of center-tapped full wave rectifier.

Background:

Simply defined, rectification is the conversion of alternating current (AC) to direct current (DC). Rectification is a process whereby an applied waveform of zero average value is changed to one that has a dc level. The process of removing one-half the input signal to establish a dc level is called half-wave rectification. The dc level obtained form half-wave rectification can be improved 100% using a process called full-wave rectification.

Apparatus:

1. Multimeter
2. Trainer with AC Power Supply
3. Bread board
4. Connecting wires
5. Resistor 1KΩ
6. Two 1N4001 Silicon Diode
7. Oscilloscope
8. 12.6V rms secondary center-tapped transformer

Formulae:

Center-taped full-wave rectifier

Output voltage (^) max = (2 x input voltage^ max) - VT

Output frequency =2 x input frequency

LAB 07

Zener diode and voltage regulation

Objectives:

1. The purpose of this experiment is to demonstrate the characteristics of a zener diode, and

Its use as a simple voltage regulator.

Background:

Zener diodes are normally reverse biased, so they maintain a constant voltage across their

terminals over a specified range of current. Like a rectifier diode, a zener diode can be approximated by a constant dc voltage source in series with a resistor. When used as a regulator, the zener diode maintains a dc output voltage that is essentially constant even though the load current may vary.

Apparatus:

1. Multimeter
2. Trainer with Variable DC Power Supply
3. Bread board
4. Connecting wires
5. Two Resistor 200Ω

6. Zener diode 6.2V
7. Oscilloscope

Formulae:

Maximum limiting series resistance

R (^) s (max) =

Zener Resistance

Rz = zener diode internal resistance = ∆Vz/∆Iz

Zener Diode current

Iz = Is - IL

Source Current

Is =

Zener diode power dissipation

Pz = IzVz

Percent load regulation

%VR = %

Where VNL = no-load (open circuit) output voltage

VFL = full-load output voltage

Procedure:

1. Wire the circuit shown in the figure 1.
2. Increase the dc supply voltage in small steps (0.5 V) while simultaneously measuring the voltage across (Vz) and the current through (Iz) the zener diode.Do not exceed a zener current of 40mA. Record your data in table 1, and plot your results for the corresponding zener current and voltage values on the graph 1 .What do you notice about the current- voltage curve for the zener diode?
3. (^) Note that initially, the zener diode current is essentially zero for the diode voltages less than the knee voltage. You should find that as the voltage drop approaches the diodes’ knee voltage, the diode current increases rapidly, while at the same time, the voltage stays essentially constant. Consequently, the zener diode maintains an essentially constant voltage drop when it is sufficiently reverse biased.
4. The 1N753 diode is rated at 6.2V with a tolerance of 10%. From your graph, determine the voltage across the zener diode .Within 10%, your value should be 6.2V. Record the measured zener voltage in table 2.

Internal Zener Resistance

Table 3:

Parameter Full Load No Load Is Iz I (^) L %VR___________________

Graph Data

LAB 08

Clipper Circuits

Objectives:

1. The purpose of this experiment is to demonstrate the operation of a diode clipper.

Background:

Diode clippers are wave-shaping circuits. They are used to prevent signal voltages from going above or below certain levels. The limiting level may be made variable with a dc source voltage.

Apparatus:

1. Multimeter
2. Trainer with AC Power Supply
3. Bread board
4. Connecting wires
5. One Resistor 15KΩ
6. 1N4001 Silicon diode
7. Oscilloscope
8. One 10KΩ Variable Resistor

Procedure:

1. Wire the circuit as shown in figure 1. Set your oscilloscope to the following settings:

Channel 1: 1 V/ division, dc coupling

Channel 2: 1 V/ division, dc coupling

Time base: 1 ms/division

Position the two lines on the oscilloscope’s display so that they are at the same level.

2. Now connect the signal generator to the breadboard. Adjust the signal generator’s output level at 6 V peak-to-peak at a frequency of 200 Hz. You should see the two waveforms similar to those shown in figure 5. Notice that the positive peaks of the clipper’s output waveform are removed, or clipped off. Notice also that the clipping levels are not perfect; the positive peaks are clipped not at zero volts, but at a small positive voltage. This is because of 0.7V voltage drop across the diode. Such an arrangement is called a positive clipper because the circuit limits the positive peaks of the input waveforms.
3. Now reverse the polarity of the diode as shown in figure 2. The behavior is opposite that of the positive clipper. The waveform has all negative peaks of the input signal removed as shown in figure 6. Again note that the clipping level is not perfect. Such an arrangement is called a negative clipper because the circuit clips off the negative peaks of the input waveform.
4. Now connect the circuit as shown in figure 3. Apply power to the breadboard and adjust the

dc voltage to +1.5 V. Connect the signal generator at 6V peak-to-peak. This time you will notice that the clipping level is higher than that measured in step2. The circuit uses a dc voltage source to bias the clipping level. This arrangement is called a positive-biased clipper. Note that the positive clipping level is the dc source voltage plus the diode’s barrier potential.

5. Vary the level of dc voltage source from 0V to 6V. You will observe that the clipping level changes with the setting of dc voltage source. When the dc bias voltage is zero, the clipping level should be the same as observed in step 2. At the other extreme there should be no clipping as the dc bias voltage is about + 6V. The diode at this extreme is effectively reverse biased and looks like an open circuit and thus input appears unchanged at the output.
6. Now connect the circuit as shown in figure 4. Adjust the dc voltage source to -1 V. Connect

the signal generator and set it at 6V peak-to-peak, to the breadboard. Note that this time the clipping level is lower than that measured in step3. The circuit uses a dc voltage source to bias the clipping level. This arrangement is called a negative-biased clipper. Notice also that the negative clipping level is the dc source voltage plus the diode’s barrier potential.

7. Vary the value of dc source from -6V to 0V. The clipping level changes with the setting of the dc source. At one extreme dc bias voltage is zero. At other extreme end, there should be no clipping .The diode is effectively reverse biased and looks like an open circuit and thus input appears unchanged at the output.

Figure 1. Positive Clipper