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ES210L, Digital Circuits and Logic Design Lab
Reporter Name: _____________________________
Date: ____________
Partner Names: _____________________________
Group No.: ___
Lab 1: 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.
What is a NOT gate?
What is an OR gate?
What is an AND gate?
What is a NAND gate?
Note: 74LS – Low-power Schottky (most popular) uses Schottky
diode clamps for protection.
https://en.wikipedia.org/wiki/7400_series
https://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits
Question: Which gate is most commonly used?
What is a NOR gate?
Figure 1. View of the some common logic packages and the pin voltages
Dr. Ali Kujoory
4/29/2017
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C. Parts needed
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A Digital Multimeter
A +5 V power supply
A breadboard/protoboard
Wires
A 74LS04 (NOT gates)
A 74LS00 (NAND gates)
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 is the absolute maximum voltage that can be applied to input?
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 input voltage of “Logical 1 = High logic?
What is the maximum input voltage of “Logical 0 = Low logic?
How many transistors do you identify in Texas Instrument 74LS04?
How many diodes (Schottky diodes) do you identify in 74LS04?
2.
Setup the circuit as shown in Fig. 2 using 74LS04 Hex Inverter. An Inverter (or NOT) gate inverts the input signal.
Using the switch and the LEDs verify the inverter function and report your observations in the table below. 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 74LS04 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.
Measure the threshold voltages 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 to +5 V using Agilent Power Supply (0 to +6V
but limit it to +5V) or through a potentiometer and the +5V Power supply available on the protoboard together with a
Digital Voltmeter to measure the input voltage. Now starting from 0V (note that U1A output is at Logical “=”
High logic), increase the voltage at the input and watch when the output at U1A makes a big change and switches
from High logic to Low logic. Call this input voltage V0H and record it in the table below. Next starting from voltage
around 4.5 V at the input (note that U1A output is at Logical “0” =Low logic), decrease the voltage and watch the
output voltage as soon as it switches from Low logic to High logic. Call this input voltage V1L and record it in the
table below. Compare these voltages with 74LS04 data sheet and conclude.
Threshold Voltage (V)
Dr. Ali Kujoory
V0H = input from low to high
4/29/2017
V1L = input from high to low
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U1A Inverter gate
Compare with 74LS04 datasheet
4.
Setup the circuit as shown in Fig. 3 using 74LS00 Quad NAND gates.
Fig 3. Two “NAND” gates with three
inputs A, B, and C
Express and simplify the output at U1B as a function of A, B, and C inputs.
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 U1B output. How would this
output compare with the output of 3-input NAND = (A.B.C)’. Use De Morgan’s Law for your proof.
A = S1
B = S2
C = S3
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Output LED
(High/Low)
(A.B.C)’
Is (ABC)’ = U1B outputs?
Why?
E. Feedback/Comments (your comments will help improving this lab)
Was the instruction clear enough? Any error?
How difficult was the experiment 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.
(*) The author acknowledges Mr. S. Marivani and as some of the sections come from his work.
Dr. Ali Kujoory
4/29/2017
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