Okay, let's sort out the main product types included in transistors. As the cornerstone of modern electronics, transistors have extremely diverse product forms, which can be mainly divided according to structure, function, power, and application scenarios:
Core understanding: A transistor is essentially a semiconductor three terminal device that utilizes the characteristics of semiconductor materials to control the flow of large currents (or voltages) through small currents (or voltages). Its core functions are signal amplification and electronic switching.
Transistors mainly include the following product categories:
Bipolar junction transistor:
Product core: A current controlled device that operates using both electron and hole carriers.
Main product form:
NPN type BJT: The most common, consisting of two layers of N-type semiconductor sandwiched by one layer of P-type semiconductor. The signal is input from the base and controls the current from the collector to the emitter.
PNP type BJT: composed of two layers of P-type semiconductor sandwiching one layer of N-type semiconductor. The working principle is similar to NPN, but the current direction is opposite (emitter to collector).
Typical application products: commonly used for signal amplification in analog circuits (such as audio amplifiers), linear regulators, switching power supplies (small and medium power), and logic circuits (early TTL). Common packaging options include TO-92 (low power), TO-126, and TO-220 (medium power).
Field effect transistor:
Product core: A voltage controlled device that utilizes electric field effects to control current. Usually, the input impedance is high and the power consumption is low. This is currently the most widely used and diverse category of transistors.
Main product forms (subdivided by structure and working principle):
Metal oxide semiconductor field-effect transistor:
N-channel MOSFET: The source and drain are N-type, and a positive voltage is applied to the gate to attract electrons and form channel conduction. The most common.
P-channel MOSFET: The source and drain are P-type, and a negative voltage is applied to the gate to attract holes and form channel conduction.
Enhanced MOSFET: default off, requires gate voltage to turn on.
Depleted MOSFET: default on, requires gate voltage to turn off (relatively rare).
Power MOSFET: A MOSFET specifically designed to handle high currents and voltages. Vertical channel design is often used in the structure (such as VDMOS), which has the characteristics of low on resistance and high switching speed. Widely used in switch mode power supplies (computer, mobile phone chargers), motor drivers (electric vehicles, drones), lighting (LED drivers), automotive electronics, inverters, etc. There are various packaging forms, such as TO-220, TO-247, D ² PAK, DFN, SOIC, etc.
Junction field-effect transistor: uses the depletion region width generated by PN junction reverse bias to control the channel conductivity. Divided into N-channel JFET and P-channel JFET. The input impedance is high, but the gain is relatively low compared to MOSFETs, and it is often used in specific applications such as high input impedance amplifiers and analog switches.
Typical application product: Almost everywhere! From billions of nanometer level MOSFETs (forming logic gates) in mobile phones and computer CPUs/GPUs, to power MOSFETs/IGBTs in power adapters and electric vehicle controllers (see below), and then to RF MOSFETs/LDMOS in RF amplifiers.
Insulated gate bipolar transistor:
Product core: A composite power semiconductor device. It combines the advantages of MOSFET voltage control (high input impedance, simple driving) and BJT low conduction voltage drop (suitable for high current).
Main product form: usually refers to high-voltage and high current power IGBT modules or single tubes.
Typical application products: The preferred choice for medium to high power switch applications, such as industrial frequency converters (drive motors), motor controllers and charging piles for electric/hybrid vehicles, high-speed rail traction systems, solar/wind inverters, induction heating equipment, high-power UPS power supplies, etc. The packaging forms are mostly modular (multiple IGBT chips and diodes integrated with a heat dissipation substrate), as well as single tube packaging (such as TO-247PLUS).
Other special types of transistors:
Darlington transistor: composed of two BJTs connected in a composite, providing extremely high current amplification. Commonly used in small signal control applications that require driving large loads (such as relay drives).
Phototransistor: The base region is sensitive to light and uses light to generate a base current to control the collector current. Used for optical detection, optical isolation (part of optocouplers), etc.
Single junction transistor: with negative resistance characteristics, mainly used in relaxation oscillators (such as early thyristor trigger circuits).
RF transistor: a transistor specifically designed for high-frequency (MHz to GHz) signal amplification, such as BJT (early), LDMOS (lateral diffusion MOSFET, commonly used in base stations), GaAs HBT/GaN HEMT (used for higher frequencies such as 5G, radar). The packaging is often a special RF packaging (such as ceramic packaging).
High electron mobility transistor: a field-effect transistor that operates using a heterojunction to form a high mobility two-dimensional electron gas, with extremely high frequency and power performance (such as GaN HEMT), and is an emerging force in fields such as 5G communication, RF power amplifiers, and efficient fast charging.
Summary and key points:
Unified core function: All transistor products revolve around the core function of "controlling high current/power with small signals" to achieve amplification or switching effects.
Main types: MOSFET (especially power MOSFET and micro MOSFET in integrated circuits) and IGBT are the most widely used and critical transistor products in electronic systems today.
Product forms are diverse: from hundreds of millions of transistors integrated into chips at the micro/nano level (forming CPUs, memories, logic ICs, etc.), to individually packaged single tubes (TO series, SOT series, etc.), and to high-power modules integrated with multiple chips (IGBT modules).
Encapsulation determines application: The encapsulation form (TO-92, SOT-23, SO-8, TO-220, TO-247, D ² PAK, module) directly reflects the power level, heat dissipation requirements, and installation method of the device.
Application driven development: The evolution of transistor products (such as from BJT to MOSFET to IGBT to GaN/SiC) has always been driven by the increasing efficiency, power density, switching speed, and cost reducing application demands.
Therefore, when it comes to "transistor products," it encompasses an extremely large family, from a few cents of general-purpose small signal BJT/MOSFET, to thousands of yuan worth of high-power IGBT modules, and even billions of micro transistors that make up the foundation of complex integrated circuits. They together form the electronic cornerstone that supports the modern digital and electrified world.