FET Fundamentals Unit 5 – Dual Gate MOSFET
MOSFETs can operate in either the depletion or enhancement mode. Some devices operate in
both modes. The dashed lines in the schematic symbol represent the enhancement mode.
Depletion mode devices are considered to be on until they are depleted, or biased off.
Enhancement mode devices are considered to be off until they are enhanced, or biased on. In this
circuit, increasing the positive bias increases drain current (ID).
NEW TERMS AND WORDS
MOSFET - metal oxide semiconductor field-effect transistor.
IGFET - insulated gate field-effect transistor.
channel - a part of a MOSFET that is continuous from drain to source and is embedded in
oppositely doped substrate material.
silicon dioxide - a glass-like oxide insulator used between the gate and channel of a MOSFET
device.