Transistor Basics: Types of Transistors & Applications

Transistors are semiconductor devices that allow for the existence of electronics that you use regularly, such as cell phones, radios, calculators and computers. There are several types of transistors to consider for different applications, so it’s crucial to understand the basic principles of how a transistor operates.

What is a Transistor?

A transistor is commonly used in electrically controlled switches or amplifiers, acting as the essential building block that regulates the operation of a circuit. With a high accuracy and response, transistors can be utilized for a large variety of functions, including switches, amplifiers, signal modulation, oscillators, and so forth.

A basic transistor has three terminals, called an emitter, base and collector. As voltage or current moves through the base, it’s modified between the emitter and collector – the emitter emitting charge carriers and the collector collecting charge carriers. The configurations for basic transistors can be either two negatively-charged terminals and one positively-charged (called NPN), or two positively-charged terminals and one negatively-charged (called PNP).

Types of Transistors

There are a variety of types of transistors that serve different purposes and vary slightly from the basic version of a transistor. Each of these transistors works for differing applications depending on the components of the circuit.

Giant Transistor (GTR):

  • Quality switching characteristics
  • High driving power
  • High voltage
  • High current
  • Complex driving circuit


  • High gain, but not too fast
  • Respond quickly
  • Photosensitive area and gain is small
  • Suitable for integration

Bipolar Transistor:

  • Commonly used in audio circuits
  • Can be divided into NPN type or PNP type depending on polarity of voltage

Bipolar Junction Transistor (BJT):

  • Both electrons are in motion simultaneously
  • Combines two PN junctions
  • Amplification function
  • Many types of BJT according to frequency

Field Effect Transistor (FET):

  • Work on the principle of field effects
  • Two main types of FET: Junction FET (JFET)and Metal-Oxide Semiconductor FETs (MOS-FET)
  • Easy integration
  • High input resistance
  • Low noise
  • Low power consumption
  • Wide dynamic range
  • Changes the magnitude of the electrical field to control the density of the conducting layer, or channel, which is modulated by voltage

Insulate Gate Bipolar Transistor (IGBT):

  • Combines GTR and Power MOSFETs
  • Good properties
  • Wide range of application
  • Three-terminal device (gate, collector and emitter)

Transistor Applications

Transistors are most commonly utilized as either amplifiers or electronic switches within a digital circuit, with each application functioning a bit differently.

Electronic Switches – The purpose of a switch is to turn on and off. For transistors, they require voltages rather than an actuator to create the on/off effect of a switch. This voltage then controls the flow of power to another part of the circuit. Transistors as switches can often be seen in applications such as memory chips, where there are millions of them turning on and off.

Amplifiers – As an amplifier, transistors take miniscule electric corrects and produce a higher current output at the opposite end. Transistors as amplifiers are most commonly used in products such as radios or hearing aids.

Contact the Experts at Solid State Inc.

Solid State Inc. is an electronic parts manufacturer, proud to offer a large variety of quality components including transistors, rectifiers, zeners, diodes and much more. If you have additional questions about types of transistors and their applications or, if you are in the market for something specific, please request a quote from us today.