LAB-01 HA11026

7/30/2019 LAB-01 HA11026

1/26

UNIVERSITI MALAYSIA PAHANGFACULTY OF MANUFACTURING ENGINEERING

BHM 2313

DIGITAL ELECTRONICS

LAB REPORT

LAB 01 : BINARY NUMBERS AND LOGIC GATES

March 30, 2013

NAME : LIM KOK WEE

STUDENT ID : HA11026

7/30/2019 LAB-01 HA11026

2/26

ABSTRACT

This lab session covers fundamental of digital

electronics, which consists of the numbering systems and logic

gates. It provides the chance for the student to implement

theoretical knowledge learnt and the practical experience for

the students to further understand the functionality of the logic

gates and some commercialized integrated circuits (IC). It is

also important for the students to familiarize with the industry

standards used as it will be useful for the digital circuit design

in their career path later. As this is the first lab session, it

provides also the opportunity for the students to learn and

familiarize the Standard Operating Procedure (SOP) of certain

lab equipment, such as oscilloscope. As a plus point of this lab

session, the students were given the chance to learn to simulate

the digital circuit using its specific software, Multisim prior to

constructing the circuit on the prototype board.

For the first part of this lab session, it covers digital

number system, which is the most basic element in digital

electronics. The experiments in this lab session focus on the

binary number system and displaying it using a seven segment

display. For the second part of this lab session, it involves

determining the output states of logic gates using oscilloscope.

With the output states determined from the oscilloscope, the

truth table for the respective logic gates can be constructed.

The logic gates used in this lab session are commercializedtransistor-transistor logic (TTL) integrated circuits (IC), in

which each contains two or more logic gates. In addition,

Boolean Algebra and DeMorgans Theorem are also being

implemented in this lab session as it is required to construct the

basic gates (AND, OR and NOT gates) using the universal

gates, which are NOR and NAND gates.

7/30/2019 LAB-01 HA11026

3/26

Page | 1

1.0 - INTRODUCTION

Digital electronics are applied in many fields, especially in the field of computer

technology. The ability of the digital circuit to count digits and perform logic functions have

made digital an important branch in electronics. Hence, it is vital for digital circuit designers

to understand the fundamental of digital electronics, which are the number systems and basic

logic gates. Generally, this lab session is aimed to expose students on the number systems

and basic logic gates. This lab session is conducted to allow students to have hands-on

experience on building digital circuits and to implement theoretical knowledge learnt in class

into this lab session. Besides that, this first lab session also provides the opportunity for the

students to learn the Standard Operating Procedure (SOP) of certain lab equipment, such as

oscilloscope. In addition, this lab session also provides the opportunity for the students to

learn to simulate digital circuits prior to construction of circuits on prototype board. This

gives a great advantage to the digital circuit designers as problems can be rectified earlier

without the need of implementing the digital circuit onto a prototype board.

Number system is the most basic element in digital electronics. There are total four

number systems used in digital electronics, which are decimal, hexadecimal, binary and octal

number systems. In fact, binary and hexadecimal are the most common used number system

in digital electronics, especially in the field of computer technology. The number systems are

interconnected and they can be converted using the specific algorithm. For the ease of codeconversion from binary to decimal, binary coded decimal (BCD) is often used as an interface

to binary number systems. It is used widely in converting binary numbers into decimal

numbers especially displaying decimal numbers in a seven-segment display. The first part of

this lab session consists of experiments generating binary numbers and displaying it as a

decimal number on a seven-segment display.

Logic gates are used in performing logic functions in a digital circuit. The most basic

logic gates are AND, OR and NOT gates. A digital circuit designer is ought to understand the

logic function of these basic gates so that the logic function of derived gates, such as NAND

and NOR gates can be understood easily. In the practical world, integrated circuits (IC) arecommonly used rather than a single logic gate. Complementary Metal Oxide Semiconductor

(CMOS) and Transistor-Transistor Logic (TTL) integrated circuits are being used in all

applications. Hence, the second part of this lab session consists of the experiments

determining the logic functions of some TTL ICs such as 7408 AND gates using oscilloscope

and thus creating its truth table. In addition, the experiments also involve the use of universal

gates, NAND and NOR gates to create the basic logic gates (AND, OR and NOT gates). This

requires the use of Boolean Algebra and DeMorgans Theorem as well in this lab session.

7/30/2019 LAB-01 HA11026

4/26

Page | 2

2.0OBJECTIVES

The objectives of this lab session are as follows:

1. To provide practical experience for the students to implement knowledge learnt in class inthe following topics :

a. Number systems, especially binary number system and binary coded decimal foreasy conversion between binary number and decimal number

b. Logic gates in the form of commercialized integrated circuits (IC)c. Constructing truth tables for logic gatesd. Boolean Algebra and DeMorgans Theoreme. Circuit troubleshooting

2. To provide a chance for students to familiarize with the industry standards used for alldigital components.

a. To obtain information from the datasheet given by the manufacturers.

3. To provide opportunity for the students to familiarize with the lab equipmenta. To learn Standard Operating Procedure (SOP) of the lab equipment

b. To learn to operate lab equipment for measurement purpose

4. To expose students to simulation of digital circuits using simulation software, NationalInstruments (NI) Multisim.

a. To learn to simulate digital circuits prior to constructing on prototype board

7/30/2019 LAB-01 HA11026

5/26

Page | 3

3.0PROCEDURES FOR EXPERIMENTS

Circuit simulation is done prior to constructing the circuits on the prototype board for

every experiment carried out in this lab session. This is to increase the productivity of the lab

session as the expected outputs have been simulated.

Experiment 1.3.1Binary Generation

Binary number can be generated by using the switch to toggle between on and offstate of

LED, which acts as the output to display the binary number generated.

List of components and instrument

1. Resistor 1k 4 pieces2. LED4 pieces3. Dual in-line package (DIP) switch4 pieces4. DC Power Supply with its connecting wire1 unit5. Digital Multimeter1 unit6. WireProcedures

1. Four bits binary number generation circuit is constructed and simulated in Multisimaccording to part of circuit given in the lab sheet as shown in Figure 1.

Figure 1 shows the part of the circuit given in

lab sheet.

Figure 2 shows the simulated circuit in

Multisim.

2. All 16 possible combinations of switch positions (0000, 0001, ,1111) are simulated andthe states of output LEDs are recorded.

3. The circuit is then constructed on a prototype board according to Figure 1 and 2. Thecircuit in Figure 1 is constructed repeatedly for four times to form circuit in Figure 2. All

four circuits share the same DC voltage source of 5V.

a. The default connection of the dual in-line package (DIP) switch is set to be openand the open configuration of the DIP switch is determined by checking the

continuity between pins of DIP switch using digital multimeter. One end of DIP

switch is connected to the 1k resistor while the other end of DIP switch is

connected to ground.

b. Anode of LED is connected to the resistor while the cathode of LED is connectedto ground.

4.

All 16 possible combinations of switch positions (0000, 0001, , 1111) are tested andthe state of switches and LEDs are recorded.

7/30/2019 LAB-01 HA11026

6/26

Page | 4

Figure 3 shows the constructed circuit list for experiment 1.3.1

5. The outputs acquired from the experiment are then analysed.Experiment 1.3.2Binary Translation

This is an extension of previous experiment. After generation of 4 bits binary number from

the previous circuit, binary numbers can be decoded using a 7447 IC, which is a binary coded

decimal (BCD) to common anode 7-segment decoder, and then displayed as a decimal digit

on a 7-segment display. Due to the use of 7447 IC, the 7-segment display must be a commonanode component as well to make sure the binary numbers are decoded correctly.

List of components

1. Resistor 1k 4 pieces2. LED4 pieces3. Dual in-line package (DIP) switch4 pieces4. 7447 IC (Common Anode) 1 unit5. 7-segment display (Common Anode)1 unit6. DC Power Supply with its connecting wire1 unit7. WireProcedures

1. Datasheet of 7-segment display is checked to make sure it is a common anode component.2. Extend previously constructed circuit in Multisim by adding a 7447 IC and a common

anode 7-segment display. The inputs for the 7447 are the four bits binary generator from

previous experiment. These inputs are connected in parallel with the LEDs

Figure 4 shows the constructed circuit in Multisim..

3. The circuit is simulated using Multisim. The states of LEDs and the outputs of 7-segmentdisplay of all 16 combinations of switch positions (0000, 0001, , 1111) are recorded.

4. Circuit for previous experiment on the prototype board is extended with 7447 IC and acommon anode 7-segment display.

a. The 4 inputs of binary number to the 7447 IC are connected parallel to the LEDs.

7/30/2019 LAB-01 HA11026

7/26

Page | 5

b. The output pins (A-G) of the 7447 IC are connected to the input pins (a-g) on thecommon anode 7-segment display.

c. To prevent from any floating inputs in a TTL IC, all unconnected pins (Pin 3 Lamp Test, Pin 4 Blanking Input/Ripple Blanking Output and Pin 5 Ripple

Blanking Input) are connected to the Vcc, which is the DC voltage source of 5V.

d. The common anode 7-segment display is then connected to Vcc.5. All 16 possible combinations of switch positions (0000, 0001, , 1111) are tested. Theoutput of LEDs and 7-segment display is recorded for each combination.

6. The outputs acquired from the experiment are then analysed.

Figure 5 shows the constructed circuit for experiment 1.3.2

Experiment 1.4TTL Logic Gates

There are in total 8 types of TTL Logic Gates Integrated Circuit given in the lab sheet. They

are 7408 Quad 2-input AND gate, 7432 Quad 2-Input OR gate, 7404 Hex Inverter, 7421 Dual

4-Input AND gate, 7425 Dual 4-Input NOR gate, 7400 Quad 2-Input NAND gate, 7402 Quad

2-Input NOR gate and 7486 Quad 2-Input XOR gate. However, the lab does not have stock

for 7425 Dual 4-Input NOR. 7425 Dual 4-Input NOR gate is replaced by equivalent gateconstructed from 7432 Quad 2-Input OR gate and 7404 Hex Inverter. To manipulate the

inputs for these gates, circuits in Figure 1 is used in this experiment. The input and output of

these gates will be represented by the state of LEDs. In addition, the pin assignments for

standard TTL logic gates integrated circuits are given in the lab sheet.

List of components and instruments

1. Resistor 1k 5 pieces2. LED5 pieces3. Dual in-line package (DIP) switch4 pieces4. 7408 Quad 2-input AND gate 1 piece5. 7432 Quad 2-Input OR gate 1 piece6. 7404 Hex Inverter1 piece7. 7400 Quad 2-Input NAND gate 1 piece8. 7402 Quad 2-Input NOR gate 1 piece9. DC Power Supply with its connecting wire1 unit10.Oscilloscope1 unit11.WireProcedures

1. Circuit for a 7408 Quad 2-input AND gate is constructed using Multisim. The 2 bitsinputs are constructed using the circuit in Figure 1. The output is represented by a LED

connected in series with a 1k Resistor. The output is then measured with anoscilloscope.

7/30/2019 LAB-01 HA11026

8/26

Page | 6

2. The circuit is simulated using Multisim. The output of LED state and oscilloscope isrecorded according the input combinations.

3. Repeat steps 1 and 2 by replacing with 7408 Quad 2-input AND gate with 7432 Quad 2-Input OR gate, 7404 Hex Inverter, 7421 Dual 4-Input AND gate, 7400 Quad 2-Input

NAND gate, 7402 Quad 2-Input NOR gate, 7486 Quad 2-Input XOR gate, 7425 Dual 4-

Input NOR gate and its equivalent gate constructed using 7432 OR and 7404 NOT gate.The number of inputs for respective TTL Logic gate IC can be increased or decreased by

adding or removing the circuit as shown in Figure 1.

Figure 6 shows the constructed circuit for equivalent 7425 Dual 4-input NOR gate in Multisim.

Figure 7 shows the constructed circuit for 7425

4-input NOR gate in Multisim.Figure 8 shows the constructed circuit for

equivalent 7425 Dual 4-input NOR gate on

prototype board.

4. Circuit for a 7408 Quad 2-input AND gate is constructed on the prototype board. Inputsare constructed based on the circuit in Figure 1. The output of AND gate is wired to a

1k Resistor and a LED.

a. Oscilloscope is set up and the positive of X10 probe is connected to the output ofthe logic gate whereas the negative of the probe is connected to the ground.

b. The outputs of LED state and oscilloscope are recorded according to the differentinput combinations.

5. Steps 4 to 6 are repeated by replacing 7408 Quad 2-input AND gate with 7432 Quad 2-Input OR gate, 7404 Hex Inverter, 7400 Quad 2-Input NAND gate, 7421 Dual 4-Input

AND gate, 7486 Quad 2-Input XOR gate, 7402 Quad 2-Input NOR gate and 7425

equivalent gate. The number of inputs for respective TTL Logic gate IC can be increased

and decreased by adding or removing the circuit as shown in Figure 1.

6. The outputs acquired from the experiment are then analysed.Experiment 1.5Truth Table

Truth table for logic gates can be constructed by using the previous circuits used in

experiment 1.4. Truth table for 7408 AND, 7432 OR and 7400 NAND gate is constructed by

7/30/2019 LAB-01 HA11026

9/26

Page | 7

acquiring the output of the logic gate through the state of LED based on different

combinations of input.


1. Resistor 1k 3 pieces2.

LED3 pieces3. Dual in-line package (DIP) switch2 pieces

4. 7408 Quad 2-input AND gate 1 piece5. 7432 Quad 2-Input OR gate 1 piece6. 7400 Quad 2-Input NAND gate 1 piece7. DC Power Supply with its connecting wire1 unit8. WireProcedures

1. Circuits for 7408 AND gates from previous experiment is constructed without presence ofoscilloscope in Multisim.

2.

Circuit is simulated and the state of output LED is recorded for every input combinations.Repeat steps 1 and 2 by replacing 7408 AND gates with 7432 OR and 7400 NAND gates.

Figure 9 shows the constructed circuit for 7408

Quad 2-input AND gate in Multisim.Figure 10 shows the constructed circuit for 7408

Quad 2-input AND gate on prototype board.

3. Circuit in experiment 1.4 for 7408 AND gate is constructed without presence ofoscilloscope in prototype board.

4. The output states of LED are recorded according to the input combinations of switchpositions.

5. Truth table is constructed using the data acquired from the experiment.6. Repeat steps 4 to 6 by replacing 7408 AND gates with 7432 OR and 7400 NAND gates.Experiment 1.5.1

Two inputs of a NAND gate will have same input. Hence, function of NAND gate will be

altered. A truth table for this function can be created through the states of output LED.


1. Resistor 1k 2 pieces2. LED2 pieces3. Dual in-line package (DIP) switch1 piece4. 7400 Quad 2-Input NAND gate 1 piece5. DC Power Supply with its connecting wire1 unit6. Wire

7/30/2019 LAB-01 HA11026

10/26

Page | 8

Procedures

1. Circuit for 7400 NAND gates with a single switch for input is constructed in Multisim.The input from the switch will act as the input for A and B in NAND gate.

2. The circuit is simulated and the states of output LED are recorded according to the input.

Figure 11 shows the constructed circuit

for experiment 1.5.1 in Multisim.

Figure 12 shows the constructed circuit for

experiment 1.5.1 on prototype board.

3. Circuit from the previous experiment using 7400 NAND gates to construct truth table ismodified. The second input of the previous circuit is removed.

a. The two inputs of 7400 NAND gates are joined and the input from the switch willact as the input for both the inputs.

4. The state of output LED is observed and recorded.5. Truth table s constructed based on the data acquired and thus the function of NAND gate

under this configuration is analysed.

Experiment 1.5.2This experiment is an extension of the experiment 1.5.1 . The 1k resistor at the input is

replaced by a 1k variable resistor so that the input voltage can be varied. Hence, the

operating region of low and high voltage can be determined from this experiment.


1. Resistor 1k 1 piece2. Variable resistor 1k 1 piece3. LED1 piece4. 7400 Quad 2-Input NAND gate 1 piece5. DC Power Supply with its connecting wire1 unit6. Digital Multimeter1 unit7. WireProcedures

1. The circuit is modified from the previous experiment in Multisim. 1k resistor in theinput is replaced with variable resistor of 1k. DIP switch and LED at the input are

removed from the circuit. Multimeter is used to measure the input voltage for the 7400

NAND logic gate.

2. The circuit is simulated. The input voltage is varied using the variable resistor andmeasured by using multimeter. The state of the output LED is being observed and

recorded as a function of input voltage.

3. The circuit is constructed on prototype board by modifying the previous circuit used inexperiment 1.5.1. LED and DIP switch are removed.

7/30/2019 LAB-01 HA11026

11/26

Page | 9

a. The end of variable resistor is connected to Vcc = 5V and ground, leaving thevoltage at the center tap to be varied.

4. The resistance of the variable resistor is measured using the digital multimeter.5. The input voltage into 7400 NAND logic gate is measured using multimeter while the

state of output LED is being observed and recorded.

6. Repeat steps 4 and 5 with the minimum, maximum resistance and the resistance thatchanges the state of output LED.


for experiment 1.5.2 in Multisim.


experiment 1.5.2 on a prototype board

Experiment 1.6Universal NORs and NANDs

NOR and NAND are universal gates, whereby any types of gates can be constructed using

them. OR gate could be constructed using only NAND gates and the truth table constructed

from the alternative circuit consists of NAND gates is similar to truth table of OR gate.


1. Resistor 1k 3 pieces2. LED3 pieces3. Dual in-line package (DIP) switch2 pieces4. 7400 Quad 2-Input NAND gate 1 piece5. DC Power Supply with its connecting wire1 unit6. WireProcedures

1.

The logic expression of the NAND gates equivalent to OR gate is derived usingDeMorgans Theorem.

A + B = .

= + = A + B

2. The circuit is similar to experiment 1.4. The circuit is constructed in Multisim by placing2 inputs, which act as the input for 7400 NAND gates. The output is determined by a

LED wired in series with a 1k resistor.

3. The circuit is simulated. The state of output LED is observed and recorded.4. The circuit is constructed on a prototype board with reference to the simulated circuit

shown in Figure 6.

5. The state of output LED is observed and recorded according to the input combinations.6. Truth table is constructed from the data acquired from the experiment.

7/30/2019 LAB-01 HA11026

12/26

Page | 10


experiment 1.6 in Multisim


experiment 1.6 on prototype board

Experiment 1.6.1Constructing AND gate using NOR gate

AND gate could be constructed using only NOR gates and the truth table constructed from

the alternative circuit consists of NOR gates is similar to truth table of AND gate.


1. Resistor 1k 3 pieces2. LED3 pieces3. Dual in-line package (DIP) switch2 pieces4. 7402 Quad 2-Input NOR gate 1 piece5. DC Power Supply with its connecting wire1 unit6. WireProcedures

1. The logic expression of the NOR gates equivalent to AND gate is derived usingDeMorgans Theorem.A . B = +

= . = A . B

2. The circuit is similar to the circuit constructed in Multisim for experiment 1.6. The 7400NAND gate is replaced by a 7402 NOR gate.

3. The circuit is simulated. The state of output LED is observed and recorded.


experiment 1.6.1 in Multisim


for experiment 1.6.1 in Multisim

4. The circuit is constructed on a prototype board with reference to the simulated circuitshown in Figure 7.


7/30/2019 LAB-01 HA11026

13/26

Page | 11

Experiment 1.6.2Constructing XOR gate using NAND gate

XOR gate could be constructed using only NOR gates and the truth table constructed from

the alternative circuit consists of NAND gates only is similar to truth table of XOR gate.


1. Resistor 1k 3 pieces2. LED3 pieces3. Dual in-line package (DIP) switch2 pieces4. 7400 Quad 2-Input NAND gate 1 piece5. DC Power Supply with its connecting wire1 unit6. WireProcedures

1. The truth table for a 7486 XOR gate is written down.2. Construct a circuit with the given expression, Q = (A. ) .(B. ) , with only 7400

NAND gates in Multisim. The input circuit is same as the circuit in Figure 1.

3. The circuit is simulated. The state of output LED is observed and recorded.


experiment 1.6.2 in Multisim.Figure 20 shows the constructed circuit for

experiment 1.6.2 on prototype board.

4. The circuit is constructed on a prototype board with reference to the simulated circuitshown in Figure 13.


7/30/2019 LAB-01 HA11026

14/26

Page | 12

4.0RESULTS AND ANALYSIS

Experiment 1.3.1Binary Generation

Binary number consists only, 0 and 1. Hence, it can be represented by the states of LED, off

and on respectively. The circuit in Figure 1 can generate binary number with the switch

triggering the state of the output LED and each circuit is considered 1 bit. Four equivalentcircuits in Figure 1, which is a 4 bit binary generation circuit, can be used to represent 16

digits numbered from 0 to 15. This can be done as the circuit has 24 = 16 combinations of

input (0000, 0001, , 1111) according to this equation, number of combination = 2n, where

n is the number of bits. The circuit in Figure 1 is an active-low circuit as the LED is on when

no input is given. When the switch is pressed, the LED is turned off.

Table 1 shows decimal number, its binary number and the switches and LEDs state observed.

Decimal

number

Binary

number

Switch; LED

1 State (MSB)

Switch; LED

2 State

Switch; LED

3 State

Switch; LED

4 State (LSB)

0 0000 On ; Off On ; Off On ; Off On ; Off

1 0001 On ; Off On ; Off On ; Off Off ; On2 0010 On ; Off On ; Off Off ; On On ; Off

3 0011 On ; Off On ; Off Off ; On Off ; On

4 0100 On ; Off Off ; On On ; Off On ; Off

5 0101 On ; Off Off ; On On ; Off Off ; On

6 0110 On ; Off Off ; On Off ; On On ; Off

7 0111 On ; Off Off ; On Off ; On Off ; On

8 1000 Off ; On On ; Off On ; Off On ; Off

9 1001 Off ; On On ; Off On ; Off Off ; On

10 1010 Off ; On On ; Off Off ; On On ; Off

11 1011 Off ; On On ; Off Off ; On Off ; On12 1100 Off ; On Off ; On On ; Off On ; Off

13 1101 Off ; On Off ; On On ; Off Off ; On

14 1110 Off ; On Off ; On Off ; On On ; Off

15 1111 Off ; On Off ; On Off ; On Off ; On

Table 2 shows comparison of some observed output and simulated output.Note : Switch on, LED off = 0 ; Switch off, LED on = 1;

Binary number : 0000 (0) Binary number : 1101 (13) Binary number : 1111 (15)

Binary number : 0000 (0) Binary number : 1101 (13) Binary number : 1111(15)

7/30/2019 LAB-01 HA11026

15/26

Page | 13

Experiment 1.3.1Binary Translation

Binary numbers can de decoded into decimal digits by a binary-coded decimal (BCD) to

common anode 7-segment display decoder (7447 IC). The segments in 7-segment display

will light up according to the seven outputs of 7447 IC and thus displaying the decimal digit.

Table 3 shows the truth table with the expected and observed output of decimal digit.Note : Switch on, LED off = 0 ; Switch off, LED on = 1;

Binary

number

Binary display segment Expected

decimal

Observed

decimal

Simulated and circuit

outputa b c d e f g

0000 on on on on on on off 0 0

0001 off on on off off off off 1 1

0010 on on off on on off on 2 2

0011 on on on on off off on 3 3

0100 off on on off off on on 4 4

7/30/2019 LAB-01 HA11026

16/26

7/30/2019 LAB-01 HA11026

17/26

Page | 15

1011 off off on on off off on

1100 off on off off off on on

1101 on off off on off on on

1110 off off off on on on on

1111 off off off off off off off No

display.

No display.

According to the result shown in the table above, only decimal digit ranging from 0

to 9 has been displayed for the binary inputs smaller than 1010. The 7-segment display

shows strange output and does not display hexadecimal digits, A to F, for binary inputs larger

than 1001.This is due to the use of binary coded decimal (BCD) to common anode display

decoder (7447 IC). Binary coded decimal (BCD) means that each decimal digit, 0 through 9,

is represented by a binary code of 4 bits. When four bits system is used, only ten code

combinations are used, which are smaller than 1010. The remaining six code combinations

(1010, 1011, 1100, 1101, 1110 and 1111) are not used and they are invalid codes in BCD

code. Hence, 7-segment display shows strange outputs for binary input more than 1001.

7/30/2019 LAB-01 HA11026

18/26

Page | 16

Experiment 1.4Logic Gates

Output of logic gates can be determined using states of output LED, logic probe or

oscilloscope. In this experiment, oscilloscope is used to determine the output states of logic

gates. In addition, truth table can also be constructed. Due to the lack of 7425 Dual 4-input

NOR logic gate, equivalent logic gate were constructed by using 7432 OR and 7404 NOT

gate using the following logic expression, Y = (A + B) + (C + D) . The equivalent gateshould produce the same truth table for 7425 Dual 4-input NOR logic gate.

Figure 21 shows that the comparison of oscilloscope reading between the circuit and simulated

circuit for 7425 4-input NOR equivalent gate with input 0000.

This figure has shown that equivalent gate produces same output as the simulated 7425 Dual

4-Input NOR gate. Hence, simulation data are the same as the circuit on prototype board.

When all inputs are to be low (0000), output of 7425 gate will produce a high output, which

turns the output LED on. As seen from Figure 21, the oscilloscope records a high voltage

when all switches are pressed to produce low inputs (0000). The default reading foroscilloscope is low voltage for output of 7425 NOR gate as all inputs are high (1111).

(a) (b) (c) (d)Figure 22 shows oscilloscope reading for (a) 7421 Dual 4-Input AND gate with input 0000 Low

Output, (b) 7402 Quad 2-input NOR gate with input 00 High Output , (c) 7400 Quad 2-input

NAND gate with input 10 High Output and (d) 7486 Quad 2-input XOR gate with input 10

High Output

Figure 22 has shown that the oscilloscope will measure the default output when no input is

given and it will show the transition between the output states when theres an input which

can cause a change in output state. Due to the high amount of outputs with these eight logic

gates, the oscilloscope reading for the output state are being tabulated into a truth table shownin Table 4.

7/30/2019 LAB-01 HA11026

19/26

Page | 17

Table 4 shows the truth table for all logic gates used in this experiment with its oscilloscope

reading.

Logic gate Input Output Oscilloscope reading

A B C D Y

7408 Quad 2-input AND gate 0 0 - - 0 Low

0 1 - - 0 Low

1 0 - - 0 Low

1 1 - - 1 High

7432 Quad 2-input OR gate 0 0 - - 0 Low

0 1 - - 1 High

1 0 - - 1 High

1 1 - - 1 High

7404 Hex Inverter 0 - - - 1 High

1 - - - 0 Low7421 Dual 4-input AND gate 0 0 0 0 0 Low

0 0 0 1 0 Low

0 0 1 0 0 Low

0 0 1 1 0 Low

0 1 0 0 0 Low

0 1 0 1 0 Low

0 1 1 0 0 Low

0 1 1 1 0 Low

1 0 0 0 0 Low

1 0 0 1 0 Low1 0 1 0 0 Low

1 0 1 1 0 Low

1 1 0 0 0 Low

1 1 0 1 0 Low

1 1 1 0 0 Low

1 1 1 1 1 High

7425 Dual 4-input NOR gate

(Obtained from equivalent gate)

0 0 0 0 1 High

0 0 0 1 0 Low

0 0 1 0 0 Low

0 0 1 1 0 Low

0 1 0 0 0 Low0 1 0 1 0 Low

0 1 1 0 0 Low

0 1 1 1 0 Low

1 0 0 0 0 Low

1 0 0 1 0 Low

1 0 1 0 0 Low

1 0 1 1 0 Low

1 1 0 0 0 Low

1 1 0 1 0 Low

1 1 1 0 0 Low1 1 1 1 0 Low

7/30/2019 LAB-01 HA11026

20/26

Page | 18

7400 Quad 2-input NAND gate 0 0 - - 1 High

0 1 - - 1 High

1 0 - - 1 High

1 1 - - 0 Low

7402 Quad 2-input NOR gate 0 0 - - 1 High

0 1 - - 0 Low1 0 - - 0 Low

1 1 - - 0 Low

7486 Quad 2-input XOR gate 0 0 - - 0 Low

0 1 - - 1 High

1 0 - - 1 High

1 1 - - 0 Low

Oscilloscope enables the easy determination of output states in a digital circuit. With the help

of oscilloscope, the output of the logic gate can actually be determined without the use of

output LED as logic indicator.

Experiment 1.5Truth tables

Truth tables for 7408 AND gate, 7432 OR gate and 7400 NAND gates are constructed based

on the outputs obtained from the experiment.

Note : Switch on, LED off = 0;

Switch off, LED on = 1;

0 = LOW;

1=HIGH;

Table 5 shows the truth table for 7408 AND gate Table 6shows the truth table for 7432 OR gate

Input Output Circuit output

A B Y = A . B

0 0 0

0 1 0

1 0 0

1 1 1


A B Y = A + B

0 0 0

0 1 1

1 0 1

1 1 1

7/30/2019 LAB-01 HA11026

21/26

Page | 19

Table 7 shows the truth table for 7400 NAND gate


A B Y = . 0 0 1

0 1 1

1 0 1

1 1 0

Experiment 1.5.1

NAND gate is one of the universal gates which is functionally complete. Many logic gates

can be constructed with NAND gates. When the two inputs of NAND gates are joined, both

inputs will have the same input from the input circuit, which is the switch. In this

configuration, the function of NAND gate will be altered and NAND gates acts as an inverter.

The following logic expression will prove the function of NAND as inverter when both

inputs are joined. Y =. =.

Table 8 shows the truth table of NAND gate as inverter consisting of circuit output and

simulated output when both inputs are joined.

Input Output Circuit output Simulated output

A Y = 0 1

1 0

7/30/2019 LAB-01 HA11026

22/26

Page | 20

Experiment 1.5.2

This experiment is done to determine the region of LOW (0) and HIGH (1) of a 7400 NAND

logic gate. The input voltage is controlled by a variable resistor of 1k. From the 7400

NAND logic gate datasheet, the LOW region should lies below 1.1V and HIGH region is

2.0V and above. The undefined region/tri-state lies in between 1.1V and 2.0V. The output for

input voltage which lies in the tri-state is unknown. Hence, in this experiment, only the LOWregion can be determined.

Table 9 shows the output as a function of input voltage.

Output state

of LED

Input voltage Resistance Circuit output

On Minimum input voltage

(LOW)

3.9 mV 1068

0.975 V 876

Off Undefined region

(Start)

1.151 V 833

Minimum input voltage

(HIGH)

undefined undefined -

Maximum input voltage

(HIGH)

4.97 V 3

7/30/2019 LAB-01 HA11026

23/26

Page | 21

According to the experiment, the minimum LOW voltage is 3.9mV which will trigger

a HIGH output. As the input voltage increases to 1.151V, which the transition from LOW

region to undefined region, the output LED is off. Due to the unknown output at undefined

region, the minimum input voltage for HIGH region cannot be determined. The maximum

input voltage for HIGH region is at 4.97V. Hence it can be derived that the operating voltage

region for 7400 NAND gate is between 3.9 mV to 4.97 V which is similar to the data fromdatasheet (0 to 5V). For the LOW region, the voltage region lies from 3.9 mV to 1.151V,

which is quite similar to the given data (0 to 1.1V).

Experiment 1.6Universal NORs and NANDs

Universal gates are gates which are functionally complete. Functional completeness means

that every possible logic gate can be realized as a network of gates of the types prescribed by

the set. In particular, all logic gates can be assembled from either only binary NAND gate or

only binary NOR gate. Hence, NAND and NOR are the universal gates. In this experiment,

OR gate is constructed using NAND gates only.

The derived logic expression of the NAND gates equivalent to OR gate usingDeMorgans Theorem is shown below :

A + B = .

= + = A + B

Table 10 shows the truth table for OR gate and the OR gate constructed using NAND gate.

OR gate OR gate constructed using NAND gate

Input Output Input Output Circuit output

A B Y = A+B A B Y

0 0 0 0 0 0

0 1 1 0 1 1

1 0 1 1 0 1

1 1 1 1 1 1

The output for the OR gate constructed using NAND gate is similar to the original OR gate.

Hence, NAND gate is a universal gate.

7/30/2019 LAB-01 HA11026

24/26

Page | 22

Experiment 1.6.1Constructing AND gate using NOR gate

This experiment is the extension of the previous topic, universal gate. NOR gate is also one

of the universal gates. Hence, other logic gates can be constructed by using it only. This

experiment involves constructing AND gate with only usage of NOR gate.

The derived logic expression of the NOR gates equivalent to AND gate using

DeMorgans Theorem is shown below :A . B = +

= . = A . B

Table 11 shows the truth table for AND gate and the AND gate constructed using NOR gate.

AND gate OR gate constructed using NOR gate


A B Y = A . B A B Y

0 0 0 0 0 0

0 1 0 0 1 0

1 0 0 1 0 0

1 1 1 1 1 1

The output for the AND gate constructed using NOR gate is similar to the original AND gate.

Hence, NOR gate is a universal gate. As a conclusion for this experiment and the previous

one, universal gates consists of only NAND and NOR gates, which are functionally complete.

Experiment 1.6.2Constructing XOR gate using NAND gate

As the previous discussion stated, NAND gate is one of the universal gates. XOR gate can beconstructed by using NAND gates only with the given logic expression, Q =(A. ) .(B. )

.

7/30/2019 LAB-01 HA11026

25/26

Page | 23

Table 11 shows the truth table for XOR gate and the XOR gate constructed using NAND gate.

XOR gate XOR gate constructed using NAND gate


A B Y = A . B A B Y

0 0 0 0 0 0

0 1 1 0 1 1

1 0 1 1 0 1

1 1 0 1 1 0

The output for the XOR gate constructed using NOR gate is similar to the original XOR gate.

7/30/2019 LAB-01 HA11026

26/26

5.0CONCLUSION

Fundamental of digital electronics covers number systems, logic gates, DeMorgansTheorem and Boolean Algebra. These basic elements will further expand digital electronics

into a sophisticated branch of electronics. This lab session expose students on these

fundamentals besides providing the opportunities to students to get familiarize with lab

equipment.

Most common used number system used in digital electronics is binary number

system, which consists only 0 and 1. It is also vital for circuit designer to understand the

concept of binary coded decimal (BCD) used for decoding binary into decimal number

system. BCD has a great advantage in binary to decimal conversion especially in a digital

circuit, which has a limited processing, for example, digital thermometer. However, BCD is

not as efficient as binary number when it involves arithmetic operation.

In addition, logic gate is the other fundamental which is covered in this lab session.There are two main category of logic gate, CMOS and TTL. In this lab session, logic gates

used are commercialized TTL logic gates integrated circuits (ICs). Information on these

industrialized ICs can be found in the datasheet provided by the ICs manufacturers such as

Renesas, Motorola, National Instruments and others. To further understand logic gates and its

function, its output has been measured using oscilloscope and truth table has been constructed.

In addition, lab does not have stock for 7425 Dual 4-Input NOR gate. Boolean algebra and

DeMorgans Theorem were implemented to obtain its equivalent gate. NAND and NOR

gates as universal gates has been introduced in this lab session as well. These gates are

functionally complete and other logic gates can be constructed by using them. There are

experiments, which involves the construction of gates using universal gates only. Hence,

Boolean algebra and DeMorgans Theorem is once again applied. In order to construct acorrect equivalent gate, truth table of the equivalent gate is constructed and compared with

the original gate.

As this lab session is the first digital lab session, it also provides the opportunity for

students to get familiarize with the lab equipment such as oscilloscope. The Standard

Operating Procedure (SOP) of the lab equipment is introduced and the way to operate the

equipment for measurement purpose is also introduced. The students also get to learn the way

to operate oscilloscope and analyse the measurement done by oscilloscope during this lab

session. The students should also learn from this lab session to set up the equipment to the

necessary setting for certain measurement to prevent output of the equipment being imprecise,

inaccurate and unreliable.

Lastly, one of the vital elements of this lab session is digital circuit simulation.

National Instruments (NI) Multisim is introduced as the simulation software. The students

were advised by lab instructor to simulate the digital circuit prior to the construction of the

circuit on prototype board. Simulation of digital circuit can greatly improve productivity of

lab session as errors in the circuit can be rectified earlier.

LAB-01 HA11026

Documents