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
What you'll learn
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.
Field Effect Transistor (FET)
A voltage-controlled semiconductor device where output current is controlled by an electric field applied via a gate terminal.
Unlike BJTs (current-controlled), FETs have extremely high input impedance (MΩ–GΩ), drawing negligible gate current. This makes them ideal for voltage amplification stages and low-power switching. Intuition: Think of a water tap where the handle (gate voltage) controls flow without needing water to leak through the handle itself.
Junction FET (JFET)
A FET where the gate-channel junction is a reverse-biased pn junction; the gate voltage modulates the channel width.
In an n-channel JFET, applying a negative gate-source voltage ( VGS ) narrows the conductive channel, reducing drain current ( ID ). At a sufficiently negative VGS (pinch-off voltage VP ), the channel is fully depleted and ID cuts off. Example: Used in analog switches and low-noise preamplifiers.
Source: Idasara knowledge pack — english/AL_SCIENCE/physics v19, short_notes: Lesson 9.5 - Field Effect Transistors (FET/JFET/MOSFET)
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