ES210, Logical Design Lab
Reporter Name:
Date:
Partner Names
Group No.:
Lab 2: Combinations of Logical Gates*
A. Objectives
1. Review the logic gates that are widely used in electronic systems
2. Review the operation of some common logic gates.
B. Introduction
A logic gate is a device that performs a logical operation on one or more logical inputs, and produces a single logical
output. Logic gates are used in most electronic systems including computers, control, communications, etc. Basic logic
gates include AND, OR, NOT, NAND, NOR. Figure 1 shows some of the common logic gates with TTL (Transistor-toTransistor) technologies. As you do each experiment write the answer to each question in the corresponding entry.
What is a NOT gate?
What is an OR gate?
What is an AND gate?
What is a NAND gate?
What is a NOR gate?
Figure 1. View of the some common logic packages and the pin voltages
Dr. Ali Kujoory
3/15/2016
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C. Parts needed
 A Digital Multimeter
 A +5 V power supply
 A breadboard/protoboard with switches and LEDs
 Wires
 A 74LS04 (NOT gate)
 A 74LS00 (NAND gate)
 Datasheets of the gates from the Internet.
D. Procedure
1. Use the datasheet of TTL gate 74LS04 by Texas Instruments and answer the following questions in the 2nd column.
What is the function of the 74LS04 gate?
How many gates are there in each package?
What the absolute maximum voltage that can be applied to any pin?
What is the nominal supply voltage of 7404?
What should be the DC voltage at pin #14 of 7404?
What should be the DC voltage at pin #7 of 7404?
What is the minimum voltage of “Logical 1 = High logic?
What is the maximum voltage of “Logical 0 = Low logic?
How many transistors do you identify in 74LS04?
How many diodes or Zener diodes do you identify in 74LS04?
2.
Setup the circuit as shown in Fig. 2 using 7404 Hex Inverter. An Inverter (or NOT) gate inverts the input signal.
Using the switch and the LEDs verify inverter function and report your observations in the following table. You can
use the LEDs on the protoboard in which case you do not need to use the 330-Ohm resistors and can connect the
outputs of the 7404 to the LEDs directly.
Fig. 2. Three NOT
gates in series.
Switch at
U1A output
Voltage
LED1
(on/off)
U2A output
voltage
LED2
(on/off)
U3A output
voltage
LED3
(on/off)
+5 V
0V
Is it what
you expect?
3.
It is desired to measure the threshold voltage at which a NOT gate switches from logical “1” to logical “0” and vice
versa. Use Fig. 2 and connect the input of Inverter U1A to a voltage between 0 V to 5 V through a potentiometer
available on the protoboard or a variable power supply together with a voltmeter to measure the input voltage. You
can use either the Agilent Power Supply (0 to +6V or 0 to +20V). Connect the output of U1A to a digital voltmeter.
Now starting from 0V (note that U1A output is at Logical 1=High logic), increase the voltage at the input and watch
the output at U1A makes a big change and switches from High logic to Low logic. Record the input voltage and call it
V0H. Next starting from voltage around 4.5 V at the input (note that U1A output is at Low logic), decrease the voltage
and watch the output voltage on the multimeteras soon as it switches from Low logical to High logic. Record the
input voltage and call it V1L. Record these voltages in the following table and compare them with the data sheet.
Dr. Ali Kujoory
3/15/2016
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Threshold Voltage (V)
V0H = input from low to high
V1L = input from high to low
U1A Inverter gate
Observation?
4.
Setup the circuit as shown in Fig. 3 using 7400 Quad NAND gates.
Fig 3. Two “NAND” gates
with three inputs A, S2, and
C
Express the output at U1B as a function of A, B, and C.
U1B output =
5.
Assume a logical variable (A, B, or C) is at “logical 1” when the corresponding switch (S1, S2, or S3) is connected to
+5 V. For each S1-S2-S3 combination record the status of the corresponding LED at the U1B output. How would this
output relate with the output of 3-input NAND = (ABC)’. Use De Morgan’s Law for your proof.
A = S1
0
0
0
0
1
1
1
1
B = S2
0
0
1
1
0
0
1
1
C = S3
0
1
0
1
0
1
0
1
LED (High/Low)
(A.B.C)’
(ABC)’ = U1B outputs? Why?
E. Feedback/Comments (your comments will help improving this lab)
Was the instruction clear enough? Any error?
How difficult was it for you?
Do you have any observations to make?
F. Report
1. In your report, keep the title of the experiment, your & your partners’ names, and your group number. Include your
measurements and answers you obtained in the tables above. Do not include the unnecessary parts such as the
objectives, instructions, and procedures.
2. Submit your report to the instructor at the end of the session.
Dr. Ali Kujoory
3/15/2016
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