Common Base Configuration:
The common base configuration is one of the three basic configurations of bipolar junction transistors (BJTs). In this configuration, the base terminal is common between the input and output, while the emitter terminal is the input and the collector terminal is the output.

Input Impedance:
Input impedance refers to the impedance seen by the signal source connected to the input of a circuit. It is a measure of how much the circuit "loads" the source. In the common base configuration, the input impedance is low.

Output Impedance:
Output impedance refers to the impedance seen by the load connected to the output of a circuit. It is a measure of how much the circuit can deliver power to the load. In the common base configuration, the output impedance is high.

Explanation:
The input impedance of the common base configuration is low because the input signal is applied to the emitter terminal, which is forward-biased. When the emitter-base junction is forward-biased, it acts as a diode and has low impedance. Therefore, the input impedance is low.

On the other hand, the output impedance of the common base configuration is high because the output signal is taken from the collector terminal, which is reverse-biased. When the collector-base junction is reverse-biased, it acts as a reverse-biased diode and has high impedance. Therefore, the output impedance is high.

The low input impedance and high output impedance of the common base configuration have certain advantages and disadvantages. The low input impedance allows for easy impedance matching with the signal source, while the high output impedance allows for better voltage amplification. However, the high output impedance can result in poor power transfer to the load.

In summary, the common base configuration of a BJT has low input impedance and high output impedance.