FREE LESSON · Semiconductors & electronics · 1 OF 4
How Semiconductors Work
From material to controllable path — Why semiconductors make switching possible
A transistor uses one electrical condition to control another.
Semiconductor behaviour can be shaped through material composition, geometry, and electric fields. In a MOSFET, voltage at an insulated gate changes whether a conductive channel forms between source and drain. The gate therefore controls current while ideally drawing little steady current itself.
“Switch” is the digital model; current, capacitance, leakage, and delay are the physical mechanism.
Why the ideal-switch picture eventually breaks
A real transistor needs time to charge and discharge capacitances. It leaks when nominally off, has resistance when on, and changes behaviour with temperature and manufacturing variation. Logic design hides much of this until speed, power, or reliability reaches a limit.
Use the simplest model that predicts the decision—then know which omitted effect becomes important next.