Introduction to Transistors, Types of Transistors and Transistor Functions

By | September 21, 2021

Definition of Transistor

Transistors in general are semiconductor components that have many functions, as amplifiers, connectors, controllers, rectifiers, signal modulators, and so on.

This component has 3 legs or three electrodes, namely the Base, Collector , and Emitter . The three legs of this transistor component certainly have different benefits but cannot be separated from each other.

Transistor comes from the word “Transfer” which means transfer and “resistor” which means resistor. So it can be concluded that the transistor is the transfer or transition of half material only to a certain temperature. If it can be likened to a current faucet that is used to drain and inhibit electric current according to the control obtained.

Transistor is a semiconductor component that is often found in various electronic circuits. In fact, almost all electronic devices have circuits that use transistor components. The various electronic devices are computers, televisions, audio players, video players, cell phones, game consoles, power supplies and so on.

The basic materials used to make transistors are Germanium, Silicon, and Gallium Arsenide. As for the packaging of the transistor components themselves, they are generally made of plastic, metal, and surface mounts. In addition, there are also several transistor components that are designed in a container commonly called an IC.

Transistor Symbol

Transistors have many symbols based on their type, Bipolar and Field Effect. The symbols possessed by Bipolar and Field Effect transistors are as follows:

Symbol of Transistor
Bipolar transistor components are divided into two types, namely:
• NPN (Negative-Positive-Negative)
• PNP (Positive-Negative-Positive)

While the Field Effect transistor, this component is divided into three types, namely:
• JFET
• MOSFET
• UJT
The picture above shows the symbols of the JFET, MOSFET, and UJT types that are owned by Field Effect transistors.

Transistor Types

In general, transistors are divided into two types, Bipolar Transistors and Field Effect Transistors. These two transistors have differences in the input and output biases they use.
Bipolar transistors require current to control the other terminals. While the Field Effect Transistor or commonly abbreviated as FET only utilizes voltage so it does not require current.

In the process of working Bipolar Transistor will require a carrier hole (charge carrier) and electrons. Whereas FET will only need one of them. Here we will review in more detail about the types of transistors and their explanations.

1. Bipolar Junction Transistor (BJT)

Bipolar Junction Transistor or commonly referred to as BJT is a type of transistor which for its structure and operation requires a charge carrier, namely electrons at the negative pole to fill the lack of electrons and holes at the positive pole.

Bipolar Junction Transistor - BJTr

Bipolar transistors have two poles that are often used in the electronics world. The Bipolar Transistor has 3 layers of semiconductor material consisting of two layers, namely the P-N-P and N-P-N layers.

The workings of this transistor consists of two diodes where the positive and negative terminals are close to each other, this is what triggers the three legs on the terminal. Changes in electric current from small amounts can cause changes in electric current in large quantities, especially at the collector terminal. So this underlies the use of resistors as electronic amplifiers.

As is well known that Bipolar Transistors are divided into two types, NPN Transistors and PNP Transistors. The following is a full explanation of the two types.

• NPN transistors are transistors that require a small electric current and a positive voltage in the base terminal to control the flow of current and a larger voltage from the collector to the emitter.

• PNP transistors are transistors that require an electric current and a negative voltage in the base terminal to control the flow of current and voltage from the emitter to the collector.

2. Field Effect Transistor (FET)

Field Effect Transistor is a type of transistor that uses electricity to control its conductivity. This type of transistor is also often referred to as a Unipolar Transistor because in the process it only uses one charge carrier, either electron or hole.

The advantages possessed by this transistor are in its quite high impedance, even for resistance both input and output reaches mega ohms. When compared to Bipolar transistors, these transistors require lower power and lower working temperature. However, this transistor has a fairly high power efficiency so the price is very expensive.
Bipolar Junction Transistor - BJT and Field Effect Transistor - FET

As with Bipolar Transistors, this type of transistor is also divided into several types. The types of Field Effect Transistors are as follows:

• Field Effect Transistor (JFET) is a transistor that generally uses a reverse biased P-N junction as an insulator between the Gate and the channel. This type of transistor is still divided into two types, namely P-channel JFET and N-channel JFET. The JFET has three terminal legs called Gate (G), Drain (D), and Source (S).

• Uni Junction Transistor (UJT) is a type of transistor that is included in the FET category. This is because in the process it also requires an electric field or voltage to control it. Unlike the typical FET type, the UJT has two base terminals (B1 and B2) and an emitter terminal as well. Here the UJT is only used as a controller (switch) and cannot be used as an amplifier as in other types of transistors.

• Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is a type of transistor that utilizes an insulator between the Gate and Channel. This MOSFET itself is further divided into two types, namely the Depletion MOSFET and the Enhacement MOSFET which is still further divided into P-Channel MOSFET and N-Channel MOSFET. MOSFET has three terminal legs, namely Gate (G), Drain (D), and Source (S). One of the things that makes a difference between a MOSFET and a FET is how to measure whether it can still function properly or not.

Transistor Function

Functions of transistor components in an electronic circuit, including:

1. Electric Current Amplifier

One of the functions of the transistor is to amplify the incoming electric current in an electronic circuit. Thus, the transistor can be used as a power supply circuit.
By using a voltage that has been regulated in such a way that the transistor can be utilized, the current needs to be biased with a constant voltage.

2. Electronic Switch

Transistor is one tool that can be used as a switch. The performance of the transistor as a switch is by adjusting the bias to saturation, so that a short connection is obtained between the emitter and the connector leg.

3. Cell Phone Signal Booster

The use of transistors on a smartphone has a main function, namely as a signal amplifier that is captured by a mobile device. In addition, transistors also store data and electric current in the electrical circuit of a smartphone.

4. Logic Gate

Transistor is a component that can be used as a switch so that it can be used as a logic gate. The logic gates that can be produced from transistor components are as follows:

• NOT
• AND
• OR
• NAND.

By becoming a switch, the transistor component is able to control the alternation of the electric current in the electronic circuit.