fotomosfet

Fotomosfet, also written photomosfet, refers to a MOSFET device whose conduction is controlled by light rather than an electrical gate voltage. In typical implementations, a MOSFET is wired to a photosensitive element such as a photodiode or a photosensitive gate material. Illumination generates charge carriers that modulate the gate potential, causing the transistor to turn on or off in response to optical signals. This makes the device inherently responsive to light and capable of optical control.

One common realization of fotomosfet is the PhotoMOS relay, which uses two MOSFETs in one package and is driven by an external LED. When the LED is energized, the MOSFETs conduct and provide a galvanically isolated switch between input and output. PhotoMOS relays are widely used as solid-state relays because they offer electrical isolation, low contact wear, and compact form factors, suitable for low- to medium-current switching tasks.

Other forms of optically controlled MOSFET devices exist for more specialized applications. Some designs incorporate a photosensitive gate that changes the MOSFET threshold or subthreshold conduction under illumination. Characteristics such as responsivity, dark current, and switching speed depend on the wavelength and intensity of light, device geometry, and packaging. Fotomosfets can provide high input impedance and optical isolation in optocoupler-based circuits, but they may require careful optical coupling, shielding from ambient light, and appropriate drive sources for the illuminating light.

See also: Phototransistor, Optocoupler, PhotoMOS relay, Optically controlled switch.