Introduction:
FET stands for Field-Effect Transistor, which is a three-terminal semiconductor device widely used in electronic circuits. It operates on the principle of the electric field effect.

Explanation:
FET has high input impedance. Let's understand why this statement is true.

What is input impedance?
Input impedance refers to the impedance seen by a signal source when it is connected to the input of a device. It is the ratio of input voltage to input current and is usually measured in ohms.

Understanding FET:
FET is a voltage-controlled device, meaning it is used to amplify and control electrical signals. It consists of a conducting channel and two pn-junctions called the source and drain. The current flow through the channel is controlled by an electric field created by the voltage applied to the gate terminal.

High input impedance of FET:
The input impedance of a FET is high due to the absence of any direct path between the input and the device's internal circuitry. This is primarily because of the reverse-biased pn-junction between the gate and the channel.

Effects of high input impedance:
1. High sensitivity: The high input impedance allows FET to pick up weak input signals with minimal loading effect. It makes FET suitable for low-power applications and sensitive amplification.

2. Minimal loading effect: The high input impedance prevents the signal source from being significantly affected by the FET circuitry. It ensures that the source signal is not attenuated or distorted due to the loading effect of the device.

3. Reduced power consumption: The high input impedance reduces the power required to drive the FET circuit because it draws very little current from the source.

4. High voltage gain: The high input impedance allows FET to provide high voltage gain since the input signal is not significantly attenuated.

5. Noise performance: The high input impedance helps in reducing the noise introduced by the FET circuit itself. It minimizes the internal noise contribution and improves the overall signal-to-noise ratio.

Conclusion:
In conclusion, FET has high input impedance due to the absence of any direct path between the input and the device's internal circuitry. This property of FET makes it suitable for various applications requiring high sensitivity, minimal loading effect, reduced power consumption, high voltage gain, and improved noise performance.