2.0
TTL Data Book
This is the manufacturer Data Book which is one of the most important books
you will use while working with integrated circuits(ICs). It tells you
all the specifications and functions of the particular chip that you need
to use to work on your experiments or projects. Also from the Data Book
you could know all the ICs that are available for use to perform the functions
that you would require for the experiments or the projects assigned.
3.0
Basic Logic Gates
A logic gate is the simplest device used to construct digital circuits.
Logic gates basically have one or more inputs and only one output. The
circuits respond to various input combinations and a truth table shows
their relationship between the input combinations and its output. familiarization
with a logic circuit's truth table is essential to the technologist or
technician before the person can design with or troubleshoot the circuit.
Various types of logic gates are available such as inverters (NOT), AND,
OR, NAND, NOR, EXOR and EXNOR, each with its own unique logic function.
3.1 NOT gate
FIGURE
1.4 NOT gate symbol.
input,
x
|
output,
y
|
0
|
1
|
1
|
0
|
TABLE 1.3 Truth TABLE
1.3 Truth table for NOT gate.Table for
NOT gate.
for 7404 IC, there are six inverters packed in a package. Each 7404 inverter
IC, has one voltage supply pin, VCC
and one ground pin, GND that provide power to all the six inverters.
3.2 OR
gate
FIGURE
1.5 OR gate symbol (2 input OR gate)
input,
x
y |
output,
z
|
0
0 |
0 |
0
1 |
1 |
1
0 |
1 |
1
1 |
1 |
TABLE
1.4 Truth table for OR gate.able for OR gate.
The two inputs OR gate available in the TTL 74 series is 7432. There are
four OR gates in this package (IC chip).
3.3 AND gate
FIGURE
1.6 AND gate symbol (Two inputs)
input,
x
y |
output,
z
|
0
0 |
0 |
0
1 |
0 |
1
0 |
0 |
1
1 |
1 |
TABLE
1.5 Truth able for AND gate
The two input AND gate available in the 74 series is 7408. There are four
AND gate in this IC chip.
3.4 NAND gate
FIGURE
1.7 NAND gate symbol (two inputs)
input,
x
y |
output,
z
|
0
0 |
1 |
0
1 |
1 |
1
0 |
1 |
1
1 |
0 |
TABLE
1.6 Truth table for NAND gate.
The output of NAND logic is actually the invert of AND. The two input NAND
gate available in the 74 series is 7400. There are also four NAND gates
in this IC chip.
3.5 NOR gate
FIGURE
1.8 NOR gate symbol (Two inputs)
input,
x
y |
output,
z
|
0
0 |
1 |
0
1 |
0 |
1
0 |
0 |
1
1 |
0 |
TABLE
1.7 Truth Table for NOR gate
The output of NOR logic is actually the invert of OR. The two inputs OR
gate available in the 74 series is 7402. There are also four NOR gates
packed in this IC chip.