Field-effect transistor

Field effect transistor is a unipolar type (with only one type of carrier participating in conduction) transistor, abbreviated as field-effect transistor, which belongs to voltage controlled semiconductor devices.

Characteristics: Field effect transistors have high input impedance, low power consumption, wide safe working area, and easy integration, making them widely used in digital circuits, communication equipment, and instrumentation.

Classification: There are two commonly used types: junction type and insulated gate type (i.e. MOS transistor), each of which is further divided into N-channel and P-channel. The three electrodes of a field-effect transistor are the source (S), gate (G), and drain (D).

The circuit symbol for field-effect transistors. Among them, N-channel junction field-effect transistor, P-channel junction field-effect transistor, P-channel enhanced insulated gate transistor, N-channel enhanced insulated gate transistor, P-channel SN74LVC257ADRG4. html "target=" -blank "title=" SN74LVC257ADRG4 ">SN74LVC257ADRG4 depletion insulated gate transistor, N-channel depletion insulated gate transistor.

1. Technical parameters of field-effect transistors: The technical parameters of field-effect transistors mainly include pinch off voltage UP (junction type), turn-on voltage UT (MOS transistor), saturated drain current II: 6S, DC input resistance, transconductance, noise figure, and maximum operating frequency.

2. Precautions for use: (1) When storing MOS devices, the three short-circuit terminals should be placed in a shielded metal box or packaged with tin foil.

(2) The extracted MOS devices cannot slide on the plastic board, and should be stored in metal trays for future use.

(3) The soldering iron used for welding must be well grounded or disconnected from the power supply and used for residual heat welding.

(4) Before soldering, the power and ground wires of the circuit board should be short circuited and separated after the MOS devices are soldered.

(5) The soldering sequence of each pin of MOS devices is drain, source, and gate. The order of disassembly is reversed.

(6) It is not possible to use a multimeter to measure the poles of MOS transistors. Testing MOS transistors requires the use of a tester.

(7) It is best to connect a protective diode to the gate of a MOSFET under permissible conditions.

(8) When using MOS transistors, special attention should be paid to protecting the gate (it should not be suspended at any time).