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The Classification of Transistors

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The invention of the transistor has brought an unprecedented impact on the electronics industry. So today’s electronic age began gorgeously. With the development of time, and then led by computers, electronic technology has achieved rapid development. Its appearance has enriched people’s lives. Today, easybom analyzes the types of transistors in detail.

Classified by Semiconductor Material and Polarity

The semiconductor materials used in transistors can be classified into germanium material transistors and silicon material transistors. Based on the polarity of this transistor could be classified in germanium NPN transistor germanium PNP transistors, silicon NPN transistors, and the silicon PNP transistor.

Classified by Structure and Manufacturing Process

Transistors can be classified into diffusion transistors planar transistors, and alloy transistors based on their design and manufacturing procedure.

Classified by Current Capacity

Transistors come in low-power, medium-power, and high-power types due to their different capacities.

Classified by Working Frequency

Transistors are classified into low-frequency transistors and high-frequency transistors as well as ultra-high-frequency transistors in accordance with the operating frequencies they use.

Classified by Package Structure

Transistors can be divided into metal packaged transistors, plastic-packaged transistors, glass packaged transistors, surface packaged transistors, and ceramic packaged transistors. There are various package shapes.

Classified by Function and Purpose

Transistors can be divided into low noise amplifier transistors, medium and high-frequency amplifier transistors, low-frequency amplifier transistors, switching transistors, high back-voltage transistors, damped transistors, phototransistors, band resistance transistors, and magnetic Sensitive transistors.

Power Transistor

Transistor for power GTR is a bipolar junction transistor that can stand up to current and high voltages. So it is sometimes called Power BJT. Its characteristics are: high withstand voltage, large current, and good switching characteristics. But its driving circuit is complicated and the driving power is large. The principle behind GTR and the bipolar junction transistors is exactly identical.


Phototransistors are optoelectronic components made up of three-terminal devices like bipolar transistors, or field-effect transistors. Light is absorbed in its active area, generating photo-generated carriers. Through the internal electric amplifying mechanism, the photocurrent gain is generated. The phototransistor works on three terminals. It is easy to realize electric control or electric synchronization. The material used in phototransistors is usually gallium arsenide. It is mainly divided into bipolar phototransistors, field-effect phototransistors, and related devices. Bipolar phototransistors usually have a high gain, but the speed is not too fast. The field-effect phototransistor is rapid response speeds. Its disadvantage is that the photosensitive area is small and the gain is small. It is often used as an extremely high-speed optical detector. There are many other planar optoelectronic devices related to this. The characteristics are fast speed and suitable for integration. Such devices are expected to be widely used in optoelectronic integration.

Bipolar Transistor

Bipolar transistor​ refers to a type of transistor that is very commonly used in audio circuits. Bipolar is derived from the relationship between current flow in two semiconductor materials. Bipolar transistors are classified as PNP or NPN types depending on the polarity of their operating voltage.

Bipolar Junction Transistor

Bipolar junction transistors are also called semiconductor transistors. This is an instrument that connects two PN junctions by a specific procedure and comes with two structures that are combined, PNP and NPN. Three poles are drawn from the outside: collector, emitter, and base. The collector is drawn from the collector area. The emitter is drawn from the launch area. The base is drawn from the base area. BJT has a magnifying effect. In order to ensure this transmission process, internal conditions must be met on the one hand. The impurity concentration of the emitter region is required to be much greater than the impurity concentration of the base region, and the thickness of the base region should be small. In addition, it needs to meet external conditions. The transmitter junction should be biased forward and the collector junction should have a reverse bias. There are many types of BJT. According to frequency, it is divided into high-frequency tubes and low-frequency tubes. According to the power, it is divided into small, medium, and high power tubes. According to semiconductor materials, it is divided into silicon tubes and germanium tubes. It is composed of amplifying circuit forms: common emitter, common base, and common collector amplifying circuit.

Field Effect Transistor

A field-effect transistor is a transistor that uses the principle of field effect. Referred to as FET. The field-effect changes the direction or magnitude of the electric field applied perpendicular to the surface of the semiconductor to control the density or type of majority carriers in the semiconductor conductive layer (channel). It modulates the current in the channel by voltage. Its working current is transported by the majority of carriers in the semiconductor. This type of transistor in which only one polarity carrier participates in conduction is also called a unipolar transistor. Compared with bipolar transistors, field-effect transistors have the characteristics of high input impedance, low noise, high limit frequency, low power consumption, a simple manufacturing process, and good temperature characteristics. It is widely used in various amplifying circuits, digital circuits and microwave circuits.

Static Induction Transistor

The static induction transistor SIT is a junction field-effect transistor. It changes the horizontal conductive structure of the low-power SIT device used for information processing to the vertical conductive structure to make a high-power SIT device. SIT is a multi-child conductive device. Its operating frequency is equivalent to or even higher than that of power MOSFET. Its power capacity is also larger than power MOSFET. Therefore, it is suitable for high frequency and high power occasions. It has been widely used in some professional fields such as radar communication equipment, ultrasonic power amplification, pulse power amplification, and high-frequency induction heating.

Single Electron Transistor

Single-electron transistors are transistors that can record signals with one or a small number of electrons. As semiconductors advance in technology and etching techniques and it is becoming easier to integrate large-scale circuits. At present, the general memory contains 200,000 electrons in each storage element, while each storage element of a single-electron transistor contains only one or a small number of electrons. This will drastically reduce power consumption and enhance the efficiency of integrated circuits.

Insulated Gate Bipolar Transistor

Insulated gate bipolar transistor combines the advantages of power transistors and power field-effect transistors. It has good characteristics. It has a wide range of applications.

Michal Pukala
Electronics and Telecommunications engineer with Electro-energetics Master degree graduation. Lightning designer experienced engineer. Currently working in IT industry.