12.11 : 電界効果トランジスタ

A field effect transistor is a three-terminal unipolar device comprising a gate, drain, and source terminal.

Charge carriers flow from the source to the drain through a channel, the conductivity of which is controlled by the potential difference applied between the gate and the source terminal.

Based on the structure of the gate diode, FETs are categorized into Junction-FETs, Metal-Semiconductor FETs, and Metal-Oxide-Semiconductor FETs.

JFETs control the channel conductivity through the extension of the gate-channel pn-junction. With their lower input impedance, they are commonly used in analog circuits.

MESFETs use metal-semiconductor diodes for rectifying contact, providing advantages such as lower temperature fabrication and lower resistance. They are used in microwave applications due to their high-frequency response.

MOSFETs, known for their high input impedance, are the most common type and are frequently used in digital circuits.

FETs can be classified further based on the channel's semiconductor material.

They are used in amplifiers, switches, and voltage regulators. Their high input impedance, compact size, low noise, and lower power consumption make them advantageous over Bipolar Junction Transistors.