MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a field-effect transistor used for signal amplification and switching control. It has a source, a drain, a gate, and an oxide insulating layer between the gate and the channel. For an enhancement-mode MOSFET, a conductive channel is formed when the gate-source voltage exceeds the threshold voltage. For a depletion-mode MOSFET, a channel already exists during manufacturing, and the gate voltage can regulate the current. In terms of characteristics, it has a high input impedance and a fast switching speed. The main parameters include threshold voltage, transconductance, drain-source breakdown voltage, etc. When applied in power amplification circuits, it can provide high-quality audio amplification. In power management circuits, it can achieve efficient power conversion. In digital circuits, as a logical element, it can fulfill data-related functions and is conducive to high-density integration.

IGBT (Insulated Gate Bipolar Transistor) is a composite device that combines the advantages of MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) and bipolar transistors. It has a gate, a collector, and an emitter. Its working principle is that a positive voltage between the gate and the emitter makes the MOSFET conduct, and then the bipolar transistor is made to conduct, thereby controlling the current between the collector and the emitter. Its characteristics include high input impedance and low on-state voltage drop. The main parameters are collector-emitter breakdown voltage, collector current rating, gate-emitter threshold voltage, etc. It is applied in industrial motor driving, inverters in power systems, motor control in electric vehicles, etc., enabling precise control, efficient conversion of electrical energy, and reduction of losses.

ACDC is a device or circuit that converts alternating current (AC) into direct current (DC). It undergoes processes such as rectification, filtering, and voltage regulation. For rectification, a diode bridge is used to convert the input AC into pulsating DC. For filtering, capacitors and inductors are employed to smooth the voltage. For voltage regulation, linear or switching voltage regulation techniques are utilized to ensure the stability of the output voltage. It has strong adaptability to input, diverse output, and a wide power range. It is widely used in fields such as consumer electronics, industry, and communication, providing suitable DC power for various types of equipment.