Questions about diodes pn junctions and zener diode True or false and explain yo
ID: 2248855 • Letter: Q
Question
Questions about diodes pn junctions and zener diode
True or false and explain your choice in a sentence or two. (a) In forward bias the drift current is the dominant mode of conduction in a pn 1. diode. (b) In reverse bias the space charge region (SCR) increases with bias. (c) Pn diode is a majority carrier device. (d) Small signal analysis does not use superposition theorem. (e) In small signal analysis the amplitude of the ac signal can be larger than the thermal voltage VT. (f A Zener diode can be used for a voltage regulator.Explanation / Answer
(a) False, in forward bias applied electric field is in oppposite direction of built-in electric field in depletion region. The net electric field is reduced thus reducing barrier to the diffusion of carriers. This results in increase of diffusion current.
(b) True, When a diode is connected in a reverse bias, the negative terminal of the battery attracts the holes in p-region away from the junction. Similarly, the electrons from n-region are attracted by the positive terminal of the battery and move away from the junction. The immobile ions in depletion region increases. Hence, a reverse biased junction has a wide depletion region
(c) False, p-n junction diode is not majority carrier device as the current flows in diode because majority carrier in forward bias and reverse saturation current flows due to minority carrier device. So, both majority and minority carrier is responsible.
(d) false, it can be used in linear and bilateral circuit.
(e) False, small signal analysis is applied only when amplitude of the input ac signal is less than the thermal voltage beacuse h-parameter varies with temperature and at high temperature they become imaginary.
(f) True, the Zener diode is called as a voltage regulated diode because it maintains a constant output voltage even though the current through it changes. A Zener diode operating in breakdown region acts as a Zener regulator (Voltage regulator) because it maintains a nearly constant voltage across its terminals.
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