~AN~ 1

LOGIC GATES

AN 2015

~AN~ 2

DIGITAL CIRCUITS

• A binary number has only 2 digits – 0

and 1. There can be a voltage

corresponding to 0 (say 0V) and 1 (say

5V). In digital electronics only these

two levels of voltages are used. Such

signals are called Digital Signals.

~AN~ 3

LOGIC GATES

• A Gate is a digital circuit that follows

certain logical relationships between the

input and output voltages. Thus, they

are generally known as logic gates.

• They consist of one or more input

signals but only one output signal.

~AN~ 4

NOT GATE or INVERTERS

• An Inverter is a gate with only 1

input signal and 1 output signal

• The output state is always the

opposite of the input state

~AN~ 5

NOT GATE

• Logic Symbol

• Boolean Expression Z = X’

~AN~ 6

AND GATE

• 2 or more input signals and 1 output

signal

• All inputs must be high to get a

high output.

~AN~ 7

AND GATE

• Boolean Expression Z = X .

Y

• Logic Symbol

X

YZ

If X is TRUE AND Y is TRUE then Z will be TRUE otherwise Z is FALSE.

~AN~ 8

OR GATE

• 2 or more input signals and 1 output

signal

• If any input signal is high, the

output signal is high.

~AN~ 9

OR GATE

• Boolean Expression Z = X +

Y

• Logic Symbol

X

YZ

If X is TRUE OR Y is TRUE then Z will be TRUE otherwise Z is FALSE.