What are the main models of transistors?

Full analysis of main transistor models: classification, characteristics, and application scenarios
Transistors, as the core components of electronic circuits, have a wide variety of models and significant performance differences, and their selection needs to be based on specific requirements. The following is a systematic review from four dimensions: technical classification, typical models, key parameters, and application scenarios.
1、 Classified by material and structure
1. Bipolar Transistor (BJT)
Representative models: 2N3904 (NPN), 2N3906 (PNP), BC547 (Universal Small Signal), TIP31 (Power Type).
characteristic:
Composed of two PN junctions, it is divided into two types: NPN and PNP.
High current amplification factor (β value 50-500), suitable for signal amplification.
Saturation voltage reduction (0.2V-1V), suitable for switch circuits.
Application: Audio amplifier, switching power supply, relay driver.
2. Field Effect Transistor (FET)
Representative models: 2N7000 (N-channel MOSFET), IRF540 (power MOSFET), BSS148 (small signal MOSFET).
characteristic:
By controlling the current through an electric field, it is divided into junction type (JFET) and insulated gate type (MOSFET).
High input impedance (>10 ^ 12 Ω), low power consumption.
Fast switching speed (nanosecond level), suitable for high-frequency scenarios.
Applications: power management, motor drive, RF amplification.
3. Insulated Gate Bipolar Transistor (IGBT)
Representative models: IRG4PH50U (600V/50A), FGA25N120 (1200V/25A).
characteristic:
Combining the advantages of BJT and MOSFET, high voltage and high current carrying capacity.
Medium switching frequency (<50kHz), suitable for medium power scenarios.
Applications: Electric vehicle inverters, industrial motor drives, induction cookers.
2、 Classified by packaging and power
1. Small signal transistor
Representative models: 2N3904 (TO-92), BC547 (SOT-23), BSS148 (SOT-23).
characteristic:
Compact packaging (such as SOT-23 size 1.7 × 1.25mm), suitable for high-density PCBs.
Low power carrying capacity (continuous current<1A), suitable for signal level applications.
Applications: Logic gate isolation, RF signal amplification, sensor signal conditioning.
2. Medium power transistors
Representative models: TIP31 (TO-220), 2N3055 (TO-3), MJE13003 (TO-126).
characteristic:
Medium power carrying capacity (continuous current of 1A-10A), withstand voltage of 50V-200V.
Moderate heat dissipation performance (TO-220 package has low thermal resistance), suitable for medium power scenarios.
Application: Switching power supply primary side, audio power amplifier, LED driver.
3. High power transistors
Representative models: IRFP460 (TO-247), FGA25N120 (TO-247), 2SC5200 (TO-3P).
characteristic:
Ultra high power carrying capacity (continuous current 10A-100A), withstand voltage 600V-1700V.
Excellent heat dissipation performance (TO-247 package has low thermal resistance), suitable for high-power scenarios.
Applications: Industrial inverters, electric vehicle charging modules, high-voltage direct current transmission.
3、 Classified by special functions
1. Darlington transistor
Representative models: TIP120 (NPN), TIP125 (PNP), ULN2003 (array).
characteristic:
Composed of two BJTs, the current amplification factor is extremely high (β value>1000).
The saturation voltage drop is relatively high (1V-2V), suitable for high current driving.
Applications: Relay driver, motor control, LED display screen.
2. Phototransistor
Representative models: PT204B (infrared receiver), LTR-303 (photosensitive), BPW34 (silicon photoelectric).
characteristic:
By combining photodiodes and transistors, optical signals are converted into electrical signals.
High sensitivity and fast response speed (microsecond level).
Application: Optoelectronic isolation, infrared remote control, photosensitive sensor.
3. Thyristor (SCR) and Triac
Representative models: BT136 (TRIAC), 2N5064 (SCR), MAC97A6 (low power).
characteristic:
Used for AC control, capable of withstanding high voltage and high current.
Maintain conductivity after triggering, suitable for switch control.
Application: Dimmer, motor speed regulation, power switch.
4、 Typical application scenarios and selection suggestions
1. Audio amplification and signal processing
Scenario: Sound system, microphone amplification, RF front-end.
Selection criteria: low noise, high bandwidth, and high linearity.
Recommended models: 2N3904 (universal), BC560 (low noise), 2SC5200 (power).
2. Power management and switch circuit
Scenario: Switching power supply, LED driver, battery charging.
Key selection points: high voltage resistance, low on resistance, fast switching.
Recommended models: IRF540 (MOSFET), IRG4PH50U (IGBT), 2N7000 (small signal).
3. Automotive Electronics and Industrial Control
Scenario: Motor driven BMS、 Electromagnetic valve control.
Selection criteria: wide temperature range (-55 ℃ to+175 ℃), high reliability (AEC-Q101).
Recommended models: 2N3904 (Universal), TIP120 (Darlington) FGA25N120（IGBT）。
4. Portable devices and low-power design
Scenario: TWS earphones, smartwatches, IoT modules.
Selection criteria: ultra-low power consumption, compact packaging, high integration.
Recommended models: BSS148 (MOSFET), BC847 (SOT-23), ULN2003 (array).
6、 Future Trends
Material innovation: Popularization of SiC/GaN devices to improve voltage resistance and high-frequency performance.
Integration: Single chip integration of transistors with driver circuits and protection circuits simplifies power supply design.
Intelligence: Programmable threshold and fault diagnosis functions are embedded to enhance system reliability.
Based on the above analysis, users can choose the most suitable transistor model according to specific scenario requirements, combined with technical parameters and cost budget.