The full name of MOSFET is Metal Oxide Semiconductor Field Effect Transistor, also commonly referred to as MOS transistor, which is one of the most core voltage controlled semiconductor devices in modern electronic systems.

Core structure and working principle
Its core consists of four key components: source (current inlet), drain (current outlet), gate (voltage control terminal), and semiconductor substrate. The gate and channel are completely isolated by a thin layer of silicon dioxide insulation.
When working, there is no need to input current to the gate. By applying different gate voltages, conductive channels can be induced on the semiconductor surface, accurately controlling the current on/off and magnitude between the source and drain. It is equivalent to an "intelligent electronic switch" that can control high currents with weak electrical signals.
Its switching speed can reach nanoseconds, input impedance can reach over 10 ¹⁰ Ω, driving power consumption is extremely low, and the on resistance has a positive temperature coefficient. When multiple devices are connected in parallel, it can automatically achieve current sharing, greatly improving reliability.

Mainstream classification methods
Divided by carrier type, it can be divided into two categories: N-channel (electron conductive, easy to drive, strong current capability) and P-channel (hole conductive). The CMOS complementary structure formed by the combination of the two is the mainstream architecture of current digital integrated circuits, and static power consumption can be almost ignored.
Divided by the channel state under zero gate voltage:
Enhanced type: When the gate voltage is zero, the channel is completely closed and a voltage exceeding the threshold must be applied to conduct. It is the most widely used type in industrial and consumer electronics.
Depletion type: When there is zero gate voltage, a conductive channel already exists and a reverse voltage needs to be applied to turn it off. It is often used in special signal processing scenarios.

Core application scenarios
With excellent switching characteristics, MOSFETs cover almost all electronic fields that require power regulation:
Digital integrated circuits: Each logic unit of chips such as CPUs and memories is built with a large number of MOSFETs, which are the physical foundation of ultra large scale integrated circuits.
In the field of power electronics, core switching devices such as mobile phone fast charging and server power supplies can improve power conversion efficiency to over 90%; It is also the core power component of new energy vehicle electronic control, industrial motor drive, and photovoltaic inverter, achieving efficient regulation of high current.
Home appliances and industrial control: air conditioning compressor speed regulation, BLDC motor drive, LED dimming, battery management system and other scenarios rely on MOSFETs to achieve precise current control, greatly reducing equipment power consumption.