Electrical Engineering › Section P · Semiconductor theory, diodes, and transistors › Topic P.12

Junction field-effect transistors: switching and active mode

A field-effect transistor controls current with a voltage instead of a current, so its control input draws almost nothing. The junction FET, the simplest kind, is normally on, turns off when its gate is reverse biased, and can act as a switch, a current regulator or a voltage-controlled resistor.