Q28 of 40 Page 92

Explain why elemental semiconductor cannot be used to make visible LEDs.

The underline principle of LED is to use the energy released in recombination of holes and electrons. All the diodes can release electro-magnetic spectrum. LED’s has a relatively lower band gap which makes them best usable for visible light emission.


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How would you set up a circuit to obtain NOT gate using a transistor?

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Write the truth table for the circuit shown in Fig.14.11. Name the gate that the circuit resembles.


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A Zener of power rating 1 W is to be used as a voltage regulator. If zener has a breakdown of 5V and it has to regulate voltage which fluctuated between 3V and 7V, what should be the value of Rs for safe operation (Fig.14.12)?