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What is a transistor?

Outline of a Transistors

Typical shapes of Transistors

(The figures show the cross-sectional views)

Mini-molded surface mounted type Transistor
Mini-molded surface mounted type transistor
Insertion type Transistor
Insertion type transistor

Transistor Map: Let us know the outline with this classification.

1.Classified according to the construction.

This is the classification based on the differences in the operating features. The classification is made as bipolar transistors and unipolar transistors.

This is the classification based on the differences in the operating features. The classification is made as bipolar transistors and unipolar transistors.

Bipolar transistors
The word bipolar consists of two roots - Bi, meaning two, and polar, meaning polarities. A bipolar transistor is one in which the current through the semiconductor forming the transistor is carried by holes (positive polarity) and electrons (negative polarity). In general, a transistor is made of silicon and is normally of this type.

This is an acronym for Field Effect Transistors. FETs can be classified into junction type FETs, MOS type FETs, and GaAs type FETs. Junction type FETs are mostly used in analog circuits such as those in audio equipment, and MOS type FETs are used mostly in digital ICs such as those used in microcomputers, etc. GaAs type FETs are used for amplification of microwaves such as satellite broadcasting receivers, etc.

This is the abbreviation for Metal Oxide Semiconductor, and the structure consists of Metal, Oxide (silicon dioxide), and Semiconductor, in that order. MOS devices are further classified into P type, N type, and C type devices, and are used in ICs with a high level of integration such as a microcomputer for reducing the current consumption.

2.Classified according to the permissible power.
Classified according to the permissible power.

This is the method of classifying the transistors based mainly on the maximum rating of the collector power dissipation Pc. The broad classification is made into small-signal transistors and power transistors. In general, a power transistor is one whose rated power dissipation is 1W or more. In particular, ROHM boasts the highest share in the industry in the field of small-signal transistors.

Small-signal transistors
These are transistors whose maximum collector current (IC(max)) is about 500mA or less and the maximum collector power dissipation (Pc(max)) is less than 1W. These transistors are called small-signal transistors to distinguish them from power transistors and have the feature that they are generally of the epoxy molded type.

Power transistors
In general, a power transistor is one that has a Pc of 1W or more. Compared to small-signal transistors, power transistors have a large maximum collector current and maximum collector power dissipation, and also have a larger size to meet the heat dissipation, and are generally shielded by metal or have a structure with heat radiating fins.

In Japan, a transistor is called a "stone". The word transistor is a combination of Transfer and resistor. Since a transistor is made of silicon which is the major element in all the rocks and stones on earth, many Japanese designers refer to a transistor as a stone.

3.Classified according to the type of integration.
Classified according to the type of integration.

Apart from discrete type transistors, ROHM is also manufacturing composite transistors integrating several transistors together, in order to meet the users' needs. These include digital transistors with built-in resistors, transistor arrays consisting of multiple transistors in one package, and transistor units with simple circuits built into them.

*Digital transistors
These are transistors with built-in resistors. The parts that are very frequently used in circuit design are standardized.

4.Classified according to the shape.
Classified according to the shape.

The size and shape of the transistor are determined by the power consumption and method of mounting. Broadly, transistors can be classified into leaded type and surface mounted type. ROHM classifies the leaded type further into general insertion type and high density insertion type, and manufactures the surface mounted type as mini-molded surface mounted type transistors.