Title: Studying different digital logic gates and designing of basic logic gates using
Universal gates.
Abstract:
To gain knowledge of characteristics of several logic gates and to get to know about
the digital trainer board and digital ICs
Part I (Basic Logic IC’s):
A set of electronic circuits on one small plate (“chip”) of semiconductor material,
normally silicon is known as integrated circuit (also referred to as an IC, a chip, or a
microchip). It is possible to make it much smaller than a discrete circuit made from
independent components. Different integrated circuits are used to implement different
logical operations in the trainer board which will be introduced in this experiment.
Theory and Methodology:
Information is translated into electric pulses varying amplitude in analog signals whereas
translation of information is in binary format (zero or one) in case of digital where each bit
represents two distinct amplitudes.
The main advantage of digital signals over analog signals is that the precise signal level of
the digital signal is not vital. This means that digital signals are fairly immune to the
imperfections of real electronic systems which tend to spoil analog signals. Codes are often
used in the transmission of information. These codes can be used either as a means of
keeping the information secret or as a means of breaking the information into pieces that are
manageable by the technology used to transmit the code. It can convey information with
greater noise immunity, because each information component (byte etc) is determined by
the presence or absence of a data bit (0 or one). Analog signals vary continuously and their
value is affected by all levels of noise. Digital signals can be processed by digital circuit
components, which are cheap and easily produced in many components on a single chip. It
uses typically less bandwidth with less electromagnetic interference. Moreover, Information
storage can be easier in digital systems than in analog ones. The noise-immunity of digital
systems permits data to be stored and retrieved without degradation.
There are two sorts of circuits which are known as integrated circuit and discrete circuit.
The two main advantages of ICs over discrete circuits are cost and performance. Cost is low
because the chips, with all their components, are printed as a unit by photolithography rather
than being constructed one transistor at a time. Furthermore, much less material is used to
construct a packaged IC die than to construct a discrete circuit. Performance is high because
the components switch quickly and consume little power (compared to their discrete
counterparts) as a result of the small size and close proximity of the components.
A logic gate is an elementary building block of a digital circuit. Most logic gates have two
inputs and one output. At any given moment, every terminal is in one of the two binary
conditions low (0V) and high (5V), represented by different voltage levels. The logic state
of a terminal can, and generally does, change often, as the circuit processes data. In most
logic gates, the low state is approximately zero volts (0 V), while the high state is
approximately five volts positive (+5 V).
There are seven basic logic gates: AND, OR, NOT, NOR, NAND,XOR and XNOR.
Different logic operations of different IC’s will be introduced which perform the following
characteristics:
AND operation:
The AND operation produces a high if and only if all the inputs are high. An AND gate can
have two or more inputs and performs AND operation or logical multiplication.
Fig1.1: Symbol of AND gate
Truth Table:
Input, A Input, B Output, F
0 0 0
0 1 0
1 0 0
1 1 1
Pin configuration for IC-74HC08N :
For a quadrature 2input AND gate HC08 davice code is used. 74HC series devices are
designed to work with a 5 V power supply, voltages from 2 V to 5 V are allowed and most
circuits work well using 5 V.
OR operation:
The OR operation produces a high output when any of the inputs are high. It has two or
more inputs and one output which performs OR operation or logical addition.
Fig 1.2: Symbol of OR gate
Truth Table:
Input, A Input, B Output, F
0 0 0
0 1 1
1 0 1
1 1 1
Pin configuration for IC-74HC32N:
HC32 is the device code. 74HC32 is a Quad 2-input OR gate (High Speed CMOS version)
which has lower current consumption/wider Voltage range from 2 to 5V. It requires low
input current of 1μA with high noise immunity characteristics of CMOS devices.
NOT operation:
The NOT operation changes one logic level to the opposite logic level. It is implemented by
a logic circuit known as an inverter.
Fig1.3: Symbol of NOT gate
Truth Table:
Input, A Output, F
0 1
1 0
Pin configuration for IC-74HC04N :
The 74HC04 is a hex inverter which consists of six inverters which perform logical invert
action. The inputs include clamp diodes that enable the use of current limiting resistors to
interface inputs to voltages in excess of VCC. The Input level for 74HC04 is CMOS level .
NAND operation:
The NAND gate operates as an AND gate followed by a NOT gate. It acts in the manner of
the logical operation "AND" followed by negation. The output will be low if both inputs are
high. Otherwise, the output is high .
Fig 1.4: Symbol of NAND
gate Truth Table:
Input, A Input, B Output, F
0 0 1
0 1 1
1 0 1
1 1 0
Pin configuration for IC-74HC00N :
HC00 is the device code. The device inputs are compatible with Standard CMOS outputs;
with pullup resistors. The operating voltage range is 2.0 to 5.0 V and low input current is 1.0
µA.
NOR operation:
The NOR gate is a combination OR gate followed by an inverter. Its output is high if
both inputs are low. Otherwise, the output is low.
Fig 1.5: Symbol of NOR gate
Truth Table:
Input, A Input, B Output, F
0 0 1
0 1 0
1 0 0
1 1 0
Pin configuration for IC-74HC02N :
The 74HC02 is a high speed Si-gate CMOS device that provides a quadrature 2 –input NOR
function. CMOS level is the input level for this sort of IC’s. The operating Voltage Range is
2.0 to 5.0 V and low input current is 1.0 µA.
XOR operation:
The XOR (exclusive OR) gate acts in the same way as the logical "either/or" .The output is
high if either, but not both, of the inputs are high. The output is low if both inputs are low or
if both inputs are high. Another way of looking at this circuit is to observe that the output is
1 if the inputs are different, but 0 if the inputs are the same.
Fig 1.6: Symbol of XOR
gate Truth Table:
Input, A Input, B Output, F
0 0 0
0 1 1
1 0 1
1 1 0
Pin configuration for IC-74HC86N :
HC86 is the device code for a quad 2-input xor gate which utilizes advanced silicon gate
CMOS technology . It maintains low power consumption and high noise immunity
characteristic of standard CMOS integrated circuits. The 74HC logic family has a voltage
range of 2V to 5V and the operating temperature is -40°C to 125°C with input current of
1µA.
XNOR operation:
The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an
inverter. Its output is high if the inputs are the same, and low if the inputs are
different.
Fig 1.7: Symbol of XNOR
gate Truth Table:
Input, A Input, B Output, F
0 0 1
0 1 0
1 0 0
1 1 1
Using combinations of logic gates, complex operations can be performed. Arrays of logic
gates are found in digital integrated circuits (ICs). As IC technology advances, the required
physical volume for each individual logic gate decreases and digital devices of the same or
smaller size become capable of performing ever more complicated operations at ever-
increasing speeds.
Apparatus:
1. Digital trainer board.
2. Integrated Circuits (ICs).
3. Power supply.
4. Connecting wires.
Integrated Circuits (ICs):
7400 : 1 pcs
7402 : 1 pcs
7404 : 1 pcs
7408: 1 pcs
7432 : 1 pcs
7486 : 1 pcs
Precautions:
The IC contains protection circuitry to guard against damage due to high static voltages
or electric fields. However, precautions must be taken to avoid applications of any
voltage higher than maximum rated voltages. For proper operation, Vin and Vout
should be constrained to the range GND (Vin or Vout) to VCC.
IC configurations:
Part II: Study of Universal Gates
A Logic Gate which can infer any of the gate among Logic Gates or a gate which can be
used to create any Logic gate is called Universal Gate. NAND and NOR Gates are called
Universal Gates because all the other gates such as NOT, AND, OR, XOR, XNOR etc can
be created by using these gates.
The Objective of this lab is to implement different logic functions using universal gates.
Theory and Methodology:
NAND gate:
The graphic symbol for the NAND gate consists of an AND symbol with a bubble on the
output, denoting that a complement operation is performed on the output of the AND gate.
Fig 2.1: Symbol of NAND gate
Output, Q= = +
It is possible to construct other gates using NAND gates which are shown in
Experimental procedure part.
Implementing various logic functions using NAND Gates:
1) Implementing NOT gate using NAND gate:
A Y
NOT gate using NAND gate
2) Implementing AND gate using NAND gate:
A
Y
B
AND gate using NAND gates
3) Implementing OR gate using NAND gate:
A
B
OR gate using NAND gates
4) Implementing XOR gate using NAND gate:
Y
B
XOR gate using NAND gates
5) Implementing XNOR gate using NAND gate:
A
Y
B
XNOR gate using NAND gates
NOR gate:
The NOR gate represents the complement of the OR operation. It’s name is an abbreviation
of NOT OR. The graphic symbol for the NOR gate consists of an OR symbol with a
bubble on the output, denoting that a complement operation is performed on the output of
the OR gate. The truth table and the graphic symbol of NOR gate is shown in the figure.
Fig 2.2: Symbol of NOR
gate Output,Q= =
Implementing various logic functions using NOR Gates:
1) Implementing NOT gate using NOR gate:
A Y
NOT gate using NOR gate
2) Implementing AND gate using NOR gate:
AND gate using NOR gates
3) Implementing OR gate using NOR gate:
A
Y
B
OR gate using NOR gates
4) Implementing XOR gate using NOR gate:
A
B
Y
XOR gate using NOR gates
5) Implementing XNOR gate using NOR gate:
A
Y
B
XNOR gate using NOR gates
Pre-Lab Homework:
Students must study the Boolean algebra rules and universal gates, perform simulation of the
circuits shown in the circuit diagram section using Power Sim 9.1.1 (PSIM) and MUST present
the simulation results to the instructor before the start of the experiment.
Apparatus:
1. Digital trainer board.
2. Integrated Circuits (ICs).
3. Power supply.
4. Connecting wires.
Precautions:
Have your instructor check all your connections after you are done setting up the circuit and
make sure that you apply only enough voltage to turn on the chip, otherwise it may get
damaged.
Experimental Procedure:
1. X-OR and X-NOR gate was constructed in the trainer board by using NAND gates only.
Required IC was used to construct the circuit.
2. The equivalent NOT, OR and AND gate was found out using NOR gates only. Then X-OR
and X-NOR gate was constructed in the trainer board using NOR gates only. Required IC was
used to construct the circuit.
3. The following expressions was converted using universal gates and implementation were done
too.
i) A (+) B
ii) (A(+)B) +C
iii) (AB +CD)’
Fig: XOR using NAND GATE
Fig: XNOR using NAND GATE
Fig: XOR using NOR gate
Simulation and Measurement:
Questions with answers:
1) Any other kind of logic gate or logic circuit can be built using a universal gate, which is a sort
of logic gate similar to NAND or NOR. This makes universal gates essential to digital circuit
design since they allow you to create all of the fundamental logic operations with a single type.
2) For an experiment involving universal gates, the required ICs typically include:
NAND Gate IC: 7400 (Quad 2-input NAND gate)
NOR Gate IC: 7402 (Quad 2-input NOR gate)
These ICs can be used to create all other basic logic gates like AND, OR, and NOT, enabling the
construction of various logic circuits.
Discussion and Conclusion:
We have used NI Multism for the simulations. While utilizing this, we had a few issues.Overall,
the software made it simple to get the answer, and the circuit drawing was mediocre for
beginners.First, we needed to understand the construction of truth tables and logic gates.After
that, we can start getting ready to work on Multisim Software. We successfully and error-free put
together every part of the Multisim bread board.We have successfully verified that there would
be no issues while connecting the circuit wires.The answer Ultimately, the data and simulations
validated our Truth-table and matched one another.
After being done with the experiment it has became easier for us to explain what is logic gate
hopefully we have gained knowledge of various logic gates as well as the digital trainer board
and digital ICs. We've studied the logic gate operations like AND Gate, OR Gate, NOT Gate,
NAND Gate, and X-OR Gate ,X-NOR Gate.
Not only that but also, we can now understand how the truth table works and how to build truth
table as well. All of our theoretical truth table findings coincided with the Simulation results.
Reference(s):
1) www.tutorialspoint.com
2) www.electronics-tutorials.ws
3) faculty.kfupm.edu.sa
4) “Digital Fundamentals” by Thomas L. Floyd
