Q. 203.8( 46 Votes )
From the information of energy band gaps of diodes, how do you decide which can be light emitting diodes?
Give any one advantage of LEDs over conventional incandescent low power lamps.
LEDs are made from direct semiconductors so that nothing else (phonons) is required. The point of the device is to create photons from an electron-hole pair and it would be highly inefficient to introduce extra energy for the electron and hole to recombine. In direct band gap semiconductors like gallium nitride most of these electrons are in the trough of the conduction band and may move to the valence band without any change in momentum from a phonon. The band gap energy of an LED can be determined by measuring the voltage across an LED at the point which the LED barely begins to turn on.
LEDs far more rugged, efficient and durable than traditional incandescent light bulbs.
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In a p-n junction diode, the current I can be expressed as
Where I0 is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, kB is the Boltzmann constant (8.6 × 10–5 eV/K) and T is the absolute temperature. If for a given diode I0 = 5 × 10–12 A and T = 300 K, then
(a) What will be the forward current at a forward voltage of 0.6 V?
(b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V?
(c) What is the dynamic resistance?
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In an unbiased p-n junction, holes diffuse from the p-region to n-region becauseNCERT - Physics Part-II
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Name the junction diode whose I-V characteristics are drawn below:
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