Electronics
Learn the key concepts of Electronics for A/L Physics, explained simply · Aligned with the NIE syllabus
Where this fits in the syllabus
Grade 2 · Term 5
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Learn the key concepts of Electronics for A/L Physics, explained simply
About A/L Physics: The A/L Physics syllabus is structured across two academic years, covering fundamental and advanced topics in mechanics, waves, electricity, and modern physics. Every topic on Idasara Academy is mapped directly to the NIE curriculum.
Bipolar Junction Transistor (BJT)
A three-terminal semiconductor device that uses both electron and hole charge carriers to amplify or switch electrical signals.
The BJT consists of two pn-junctions formed by three doped regions: emitter, base, and collector. It is called "bipolar" because both majority and minority carriers contribute to current flow. In amplifiers, a small base current controls a much larger collector current.
NPN vs. PNP Transistors
NPN has a p-type base sandwiched between two n-type regions; PNP has an n-type base between two p-type regions.
In NPN, electrons are the majority carriers in the emitter and collector; in PNP, holes are the majority carriers. Circuit symbols differ by the arrow direction on the emitter (pointing out for NPN, in for PNP). For Sri Lankan syllabus, NPN is more commonly used in examples.
Source: Idasara knowledge pack — english/AL_SCIENCE/physics v19, short_notes: Lesson 9.4 - Bipolar Junction Transistors (BJT)
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