What is bipolar transistor? - Definition from WhatIs.com


bipolar transistor

Part of the Microprocessors glossary:

See also field-effect transistor (field-effect transistor) and transistor.

A bipolar transistor is a semiconductor device commonly used for amplification. The device can amplify analog or digital signals. It can also switch DC or function as an oscillator. Physically, a bipolar transistor amplifies current, but it can be connected in circuits designed to amplify voltage or power.

There are two major types of bipolar transistor, called PNP and NPN. A PNP transistor has a layer of N-type semiconductor between two layers of P-type material. An NPN transistor has a layer of P-type material between two layers of N-type material. In P-type material, electric charges are carried mainly in the form of electron deficiencies called holes. In N-type material, the charge carriers are primarily electrons.

The bipolar transistor has advantages and disadvantages relative to the field-effect transistor (field-effect transistor). Bipolar devices can switch signals at high speeds, and can be manufactured to handle large currents so that they can serve as high-power amplifiers in audio equipment and in wireless transmitters. Bipolar devices are not especially effective for weak-signal amplification, or for applications requiring high circuit impedance.

Bipolar transistors are fabricated onto silicon integrated circuit (IC) chip. A single IC can contain many thousands of bipolar transistors, along with other components such as resistors, capacitors, and diodes.

This was last updated in April 2005
Posted by: Margaret Rouse

Related Terms


  • system-on-a-chip (SoC)

    - System-on-a-chip (SoC) technology is the packaging of all the necessary electronic circuits and parts for a "system" (such as a cell phone or digital camera) on a single integrated circuit (IC), ge... (WhatIs.com)

  • holographic processing unit (HPU)

    - Holographic processing unit (HPU) is what Microsoft has named the coprocessor in its HoloLens virtual reality (VR) headset. The HPU conducts the processing that integrates real world and data for a... (WhatIs.com)

  • quad-core processor

    - A quad-core processor is a chip with four independent units called cores that read and execute central processing unit (CPU) instructions such as add, move data, and branch. (WhatIs.com)


  • Microprocessors

    - Terms related to microprocessors, including definitions about silicon chips and words and phrases about computer processors.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About bipolar transistorPowered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment



    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.