# Analysis and Design of Combinational and Sequential circuits

**1. Analysis and Design of Combinational circuits:**

To design of combinational circuits, the procedure involves the following steps:

- Find the required number of inputs and outputs and assign a symbol to each.
- Derive the truth table according to given specifications and function.
- Using the truth table, obtain simplified Boolean functions for each output as a function of the input variables.
- Draw the logic circuit diagram.

To obtain the output Boolean functions from a logic diagram, the procedure involves the following steps:

- Label all gate outputs with unique symbols.
- Find the Boolean functions for these gates.

To obtain the truth table directly from the logic diagram, the procedure involves the following steps:

- Determine the number of input variables in the circuit.
- Draw the table for these inputs. There are 2^n combinations for the n input variables (0 to (2^n -1)).
- Label the outputs with unique symbols for gates in the circuit.
- Obtain the outputs of these gates in the table.

**Drawbacks of Combinational circuits:**

If you need to design a system that stores and uses previous input and output, then we can not use a combinational circuit because it doesn’t have capability to store any state or depend clock or and time. For these properties you can use Sequential circuits.

**2. Analysis and Design of Sequential circuits:**

To design of Sequential circuits, the procedure involves the following steps:

- Derive the state table and state equations.
- Derive the state diagram using the state table.
- Reduce states using state reduction technique.
- Verify the number of Flip-Flops and type of Flip-Flop to be used.
- Derive the excitation equations using the excitation table.
- Derive the output function and the Flip-Flop input functions.
- Derive the logic functions or equation for each output variable.
- Draw the required logic diagram.

Examples of sequential circuits are Registers, Shift Registers, Counters, Ripple Counters, Synchronous Counters etc.

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