IC
7404 – 2 Input -NOT Gate
IC
7432 – 2 Input -OR Gate
IC
7408 - 2 Input -AND Gate
IC7400-
2 Input -NAND Gate
IC7402
- 2 Input -NOR Gate
IC7486
– Quad 2 Input –EX-OR Gate
IC74266 – Quad 2 Input –EX-NOR Gate
Introduction to
Digital Logic Gates :A Digital
Logic Gate is an electronic device that makes logical decisions based on
the different combinations of digital signals present on its inputs. A digital
logic gate may have more than one input but only has one digital output.
Standard commercially available digital logic gates are available in two basic
families or forms, TTL which stands for Transistor-Transistor
Logic such as the 7400 series, and CMOS which stands
for Complementary Metal-Oxide-Silicon which is the 4000 series of
chips. This notation of TTL or CMOS refers to the logic technology used to
manufacture the integrated circuit, (IC) or a "chip" as it is more
commonly called.
Classification of Integrated Circuits
Classification of Integrated Circuits
1. Small Scale Integration or (SSI) -
Contain up to 10 transistors or a few gates within a single package such as
AND, OR, NOT gates.
2. Medium Scale Integration or (MSI) -
between 10 and 100 transistors or tens of gates within a single package and
perform digital operations such as adders, decoders, counters, flip-flops and
multiplexers.
3. Large Scale Integration or (LSI) -
between 100 and 1,000 transistors or hundreds of gates and perform specific
digital operations such as I/O chips, memory, arithmetic and logic units.
4. Very-Large Scale
Integration or (VLSI) - between 1,000 and 10,000 transistors or
thousands of gates and perform computational operations such as processors,
large memory arrays and programmable logic devices.
5. Super-Large Scale
Integration or (SLSI) - between 10,000 and 100,000 transistors
within a single package and perform computational operations such as
microprocessor chips, micro-controllers, basic PICs and calculators.
6. Ultra-Large Scale
Integration or (ULSI) - more than 1 million transistors - the
big boys that are used in computers CPUs, GPUs, video processors,
micro-controllers, FPGAs and complex PICs.
Digital
Logic States : The Digital Logic Gate is the basic building block from which
all digital electronic circuits and microprocessor based systems are constructed
from. Basic digital logic gates perform logical operations of AND, OR and NOT on binary
numbers.
In digital logic design only two
voltage levels or states are allowed and these states are generally referred to
as Logic
"1" and Logic "0", High and Low, or True and False. A good
example of a digital signal is a simple light as it is either "ON" or
"OFF" but not both at the same time.
The Logic
"AND" Gate :
A Logic AND Gate is
a type of digital logic gate that has an output which is normally at logic
level "0" and only goes "HIGH" to a logic level "1"
when ALL of its inputs are at logic level
"1". The output state of a "Logic AND Gate" only returns
"LOW" again when ANY of its inputs are at a logic level
"0". In other words for a logic AND gate, any
LOW input will give a LOW output.
The logic or Boolean expression given
for a logic AND gate is that for Logical
Multiplication which
is denoted by a single dot or full stop symbol, ( . )
giving us the Boolean expression of: A.B = Q.
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