2. Objectives
Perform the three basic logic operations.
Describe the operation of and construct the truth tables
for the AND, NAND, OR, and NOR gates, and the NOT
(INVERTER) circuit.
Write the Boolean expression for the logic gates and
combinations of logic gates.
Implement logic circuits using basic AND, OR, and
NOT gates.
3. Objectives
Use either of the universal gates (NAND or NOR) to
implement a circuit represented by a Boolean
expression.
Explain the advantages of constructing a logic-circuit
diagram using the alternate gate symbols versus the
standard logic-gate symbols.
Describe the concept of active-LOW and active-HIGH
logic symbols.
4. Boolean Constants and Variables
Boolean 0 and 1 do not represent actual
numbers but instead represent the state, or
logic level.
Logic 0 Logic 1
False True
Off On
Low High
No Yes
Open switch Closed switch
8. IN CASE OF NOT GATE OUTPUT IS NOT AS
INPUT.
IN CASE OF AND GATE, OUTPUT WILL BE
ONE IF A AND B, ARE ONE
IN THE CASE OF OR GATE, OUTPUT WILL
BE ONE IF A OR B IS ONE.
9. Truth Tables
A truth table is a means for describing how a
logic circuit’s output depends on the logic
levels present at the circuit’s inputs.
Inputs Output
A B x
0 0 1
0 1 0
1 0 1
1 1 0
?
A
B
x
10. Logic Gates and there IC numbers
AND – IC 7408
OR – IC 7432
NOT – IC 7404
NOR – IC7402
NAND – IC 7400
XOR – IC 7486
14. Poll Question
Q2. If both the inputs of OR gate are high then
what will be the output?
a) 0
b) 1
c) Both a and b
d) None of these
15. Poll Question
Q3. The logic gate that will have HIGH or "1" at its output
when any one of its inputs is HIGH
a) NOR gate
b) AND gate
c) OR gate
d) NOT operation
