Active devices


Basic electronic components, the operation of which depends on an external power supply, are called active components. They can amplify signals and / or process signals. Some active components are transistors, integrated circuits.


A transistor is a nonlinear semiconductor. The transistor is considered one of the most important devices in electronics. The transistor has changed many aspects of human life. Transistors have two main functions, which amplify the input signals and act as semiconductor switches. The transistor acts as a switch when used in the saturation or interruption interval. Amplifies signals when used in the active area. It offers a very high input resistance and a very low output resistance.

Transistors are classified according to the structure of bipolar transverse transistors and field effect transistors.

Transistor symbol

The most popular and commonly used transistors are BC547, 2N2222. Below are some common transistor packages:

A metal oxide semiconductor field effect transistor (MOSFET) is a semiconductor device that differs in structure from a bipolar junction transistor, although the applications are the same as coupling and amplification. It has four terminals such as Drain, Gate, Source and Body. The chassis is short-circuited to the source socket. The gate is insulated from the pipe next to a very thin layer of metal oxide. Therefore, it offers a very high durability compared to BJT.

By checking the gate voltage (VGS + ve / -ve) of the channel along which the charge carriers (electrons or holes) flow from the source to the channel, the width can be checked. P-channel MOSFET has a P-channel area between the source and channel, and N-channel MOSFET has an N-channel area.

The advantages of MOSFET over BJT

  • Very high resistance to entry
  • Reduced opposition to the state
  • Reduced energy losses
  • High operating frequency
  • Transistor operation
  • Transistor operation
  • Use of transistors (BJT / FET)

Amplification of analog signals.

Used as replacement units in SMPS, microcontrollers, etc.
Overvoltage / undervoltage protection
signal modulation and demodulation circuits.
Current control in converters and chargers (high power transistors)
Types of transistor packages

For BJT and MOSFET packaging, the transistors are available in orifice (DIP) and SMD versions. for example, DIP: TO-92, TO-220 and SMD: SOT23, SOT223, TO-252, D2PAK.

Transistor selection parameters

When selecting a transistor in any user of the circuit, consider the following parameters

  • Maximum collection current (Ic)
  • Maximum collector voltage (Vce)
  • VBE voltage
  • Saturation Vce (village) tension
  • Current gain, hfe / ß
  • Input resistor
  • The first answer
  • Reverse distribution voltage
  • Maximum return current.
  • Evaporation of force
  • Interface temperature
  • size
  • Switching time / frequency

Integrated circuits

An integrated circuit (IC) is an electronic circuit embedded in a semiconductor board, which is usually silicon. This disk has millions of compact transistors, resistors and capacitors connected to metal strips. ICs are powered by an external power supply for operation. ICs perform certain functions, such as data processing and signal processing. The physical size of an IC disk is very small compared to discrete circuits, so it is called a microchip or just a chip. Due to its small size, the IC has low power consumption.

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