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CBSE Class 12 · 2004 · SemiconductorsShort Answer

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With the help of a diagram, show the biasing of a light emitting diode (LED). Give its two advantages over conventional incandescent lamps.

Solution

An LED is operated in forward bias: the p-side is connected to the positive terminal and the n-side to the negative terminal through a current-limiting resistor.
On forward bias, electrons and holes recombine at the junction and the released energy is emitted as light.
Advantages over an incandescent lamp: (i) it operates at low voltage and consumes very little power; (ii) the emitted light is nearly monochromatic and the device has a fast response with long life.

CBSE Class 12 Board · 2004 · Subjective

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