electrical4u.com logo Home MCQ Engineering Calculators Videos Basic Electrical Circuit Theories Electrical Laws Materials Batteries Illumination Generation Transmission Distribution Switchgear Protection Measurement Control System Utilities Safety Transformer Motor Generator Electrical Drives Electronics Devices Power Electronics Digital Electronics Biomedical Instrumentation

Types of Transistor

Published on 24/2/2012 & updated on 11/11/2018

Classification Based on Transistor Structure

Point Contact Transistors

These were the very-first Germanium transistors, which worked based on the basis of a difficult and unreliable electrical forming process, causing them fail quite often. Further, they had a common-base current gain α greater than 1 and exhibited negative resistance.transistor

Bipolar Junction Transistor (BJT)

BJTs are the transistors with three terminals (Emitter, Base and Collector) and hence possess two-junctions viz., Base-Emitter junction and Collector-Base junction. These are current-controlled devices whose conduction current relies on both majority as well as minority charge carriers (hence bipolar). Bipolar Junction Transistor BJTFurther, these can be either (i) npn with majority charge carriers as electrons or (ii) pnp with majority charge carriers as holes, depending on their doping nature. Apart from these, many other types of BJTs found are

Related pages
Types of Transistor

Field Effect Transistor (FET)

These are the voltage-controlled transistors which are tri-terminal wherein the Gate terminal controls the flow of current between the Source and the Drain terminals. These are also called unipolar devices as their conduction current is only due to the majority charge carriers according to which they can be either n-channel (the majority charge carriers are electrons) FETs or p-channel (the majority charge carriers are holes) FETs. Further, FETs can be classified asField Effect Transistor FET

Classification Based on their Function

  1. Small Signal Transistors:

    These type of transistors are particularly used to amplify the low level signals (rarely for switching) and can be either npn or pnp in nature.
  2. Small Switching Transistors:

    These are extensively used for switching purposes although they can be employed for amplification process. These transistors are available in both npn as well as pnp forms.
  3. Power Transistors:

    These are used as power amplifiers in high power applications and can be npn or pnp or Darlington transistors.
  4. High Frequency Transistors:

    These are also known as RF Transistors and are used in high speed switching devices wherein the small signals operate at high frequencies.
  5. Photo-Transistor:

    These are two-terminal light-sensitive devices are nothing but the standard transistors which have photosensitive region as a substitute for the base region.
  6. Unijunction Transistors:

    These transistors are exclusively used as switches and are not suitable for amplification.
  7. Biomedical and Environmental Transistors:

    These are used in the field of biomedicine and environmental sensing.

In addition to these, there also exists an Insulated-Gate Bipolar Transistor (IGBT) which combines the features of both BJTs as well as FETs as it uses an insulated gate to control a bipolar power transistor acting as a switch. There are also devices which comprise two tunneling junctions enclosing a gate-controlled island called Single Electron Transistors (SETs). Certain transistors like those of junctionless Nanowire Transistor (JNT) even lack the presence of gate junction which leads to denser and cheaper microchips. Lastly, it is to be noted that these are just a countable number of transistor types amongst the ample types present in the market.

Please Rate this Article
⚑ 1 total

New Articles
More Articles on Electronics Devices
SemiconductorPrinted Circuit BoardBasic ElectronicDiodeJFETLight Emitting DiodeZener DiodeRectifierTheory of Diode MosfetAmplifierMultivibrators
Articles Categories
Basic Electrical
Electric Transformer
Electric Generator
Electric Motor
Electrical MCQ
Engineering Calculators
Video Lectures
Electrical Generation
Electric Transmission
Electric Protection
Electrical Measurement
Electronics Devices
Power Electronics
Digital Electronics