Sequential circuits have outputs determined by both the current inputs and previous outputs due to the inclusion of memory elements. Combinational circuits only have outputs determined by the current inputs. Sequential circuits contain logic gates arranged in parallel and feedback loops allowing the circuit to store past states, while combinational circuits only depend on the current input combination. There are different types of sequential circuits including those controlled by a clock signal from a clock generator that produces periodic pulses defining the circuit timing.

1. SEQUENTIAL CIRCUITS
By Unsa Shakir

2. Circuits

3. Combinational vs Sequential Circuit
A
B
F
C
D
Combinational Circuit
- output determined
solely by inputs
Sequential Circuit
- output determined by
inputs AND previous
outputs
A
B
F
C

4. 4
• Combinational Logic circuit contains logic gates where its
output is determined by the combination of the current
input, regardless of the output or the prior combination of
input.
n input m output
combinational
circuit
Combinational Circuit

5. 5
• Sequential Logic Circuit contains logic gates arranged in
parallel and its output is not only determined by the
combination of the current input, but also the prior output.
• The circuit also contains memory elements that enable it to
store the information of the prior output.
Sequential Circuit
n input
m output
sequential
logic
circuit
memory
elements

7. Sequential Logic: Concept
• Sequential Logic circuits remember past inputs
and past circuit state.
• Outputs from the system are
“fed back” as new inputs
• With gate delay and wire delay
• The storage elements are circuits that are
capable of storing binary information: memory.

8. Sequential Circuit Types

9. Sequential Circuit Types
Sequential Circuits

10. Clock
Sequential Circuits

12. 2017/12/19 PJF - 9
Sequential Circuits
Clock Signal
Different duty cycles
Clock generator: Periodic train of clock pulses