1. LECTURE ON COMBINATIONAL AND
SEQUENTIAL CIRCUITS
BY,
DEEPIKA GOTTIPATI

2. COMBINATIONAL CIRCUITS
 Output is dependent only on input
 Doesn’t contain memory element
 Value of present output is determined by present
input
 Examples of combinational circuits are half adders,
full adders, subtractors etc

3. SEQUENTIAL CIRCUITS
 Outputs depend on present inputs and previous
inputs also
 It contains memory elements for storing previous
state inputs
 Examples of sequential circuits are flip flops,
counters, shift registers

4. GATES
 AND
 NAND
 OR
 NOR
 NOT
 EX-OR
 EX-NOR

5. UNIVERSAL GATES
 The basic building blocks of any design are
UNIVERSAL GATES
 NAND and NOR are the universal gates

6. FUNCTIONALITY OF NAND GATE
 The NAND function is a combination of the two
separate logical functions, the AND function and the
NOT function connected together in series.
 The logic NAND function can be expressed by the
Boolean expression of, A.B
 The Logic NAND Function only produces the output
when any of its inputs are FALSE.

7. NAND GATE
2 INPUT NAND GATE TRUTH TABLE

8. FUNCTIONALITY OF NOR GATE
 The NOR Gate is also a combination of two
separate functions, the OR function and the NOT
function connected together in series
 The logical NOR function is expressed by the
Boolean expression as, A + B
 The Logic NAND Function only produces the output
when all of its inputs are FALSE

9. NOR GATE
2 INPUT NOR GATE TRUTH TABLE

10. HOW TO DESIGN A COMBINATIONAL CIRCUIT
 Half adder
 truth table
 K-Maps
 Circuit using gates

11. HOW TO DESIGN A SEQUENTIAL CIRCUIT
[FLIP FLOPS]
 SR Flip flop
 JK Flip flop
 D Flip flop
 T Flip flop