Master-Slave Flip-flop is used to avoid race around problems.

Race around problem:
A race around problem occurs in sequential circuits when the output of a flip-flop changes before the input pulse has been completely applied and settled. This results in unpredictable and incorrect behavior of the circuit.

Explanation:
Master-Slave Flip-flop is a type of flip-flop that consists of two separate flip-flops, namely the master flip-flop and the slave flip-flop. The master flip-flop is responsible for accepting the input signal and the slave flip-flop is responsible for producing the output signal.

To understand why the Master-Slave Flip-flop is used to avoid race around problems, let's look at the working principle of this flip-flop.

Working Principle of Master-Slave Flip-flop:
1. The master flip-flop is triggered by the clock signal, and its output changes according to the input signal.
2. However, the output of the master flip-flop does not directly affect the output of the overall flip-flop circuit.
3. The output of the master flip-flop is fed into the slave flip-flop only when the clock signal is in the opposite state (e.g., if the master flip-flop is triggered by the rising edge of the clock signal, the slave flip-flop is triggered by the falling edge of the clock signal).
4. The output of the slave flip-flop is the final output of the flip-flop circuit.

By using this two-stage approach, the Master-Slave Flip-flop effectively avoids race around problems. Here's why:

1. The master flip-flop only changes its output when the clock signal triggers it. This ensures that the input signal is applied and settled before any changes occur.
2. The slave flip-flop only samples the output of the master flip-flop when the clock signal is in the opposite state. This further ensures that the output of the flip-flop circuit is stable and predictable.

Therefore, by using the Master-Slave Flip-flop, race around problems can be avoided as the input signal is properly captured and settled before any changes occur in the output.