utarmningslägesMOSFET

An utarmningslägesMOSFET, known in English as a depletion-mode MOSFET, is a type of Metal-Oxide-Semiconductor Field-Effect Transistor. Unlike enhancement-mode MOSFETs, which require an applied gate voltage to create a conductive channel, depletion-mode MOSFETs are designed to have a conductive channel present even with zero gate-source voltage.

The structure of a depletion-mode MOSFET is similar to an enhancement-mode device, typically featuring a semiconductor substrate, a gate electrode, a gate dielectric (like silicon dioxide), and source and drain regions. However, the channel region is either doped in such a way that it is naturally conductive, or a built-in doping profile creates a channel.

When a negative gate-source voltage is applied to an n-channel depletion-mode MOSFET, it repels the majority carriers in the channel, reducing its conductivity and thus the drain current. This is why it is called "depletion mode" – the applied voltage depletes the mobile charge carriers from the channel. Conversely, a positive gate-source voltage can further enhance the channel conductivity, increasing the drain current, similar to an enhancement-mode device.

The opposite behavior is observed in a p-channel depletion-mode MOSFET, where a positive gate-source voltage depletes the channel, and a negative voltage can enhance it. These transistors are often used in applications where a normally-on switch is required, or in certain amplifier circuits.