Interview Questions- MBA Admissions- Job Interviews
- Electronics and Communication, Applied Electronics
• How many type of resistances are there in a diode
Two, one when forward biased have zero resistance and the other when reverse biased has infinite resistance
• What is zero crossing rate ?
The zero-crossing rate is the rate of sign-changes along a signal, i.e., the rate at which the signal changes from positive to negative or back. This feature has been used heavily in both speech recognition and music information retrieval
• Define super conductivity
Superconductivity is a phenomenon occurring in certain materials at extremely low temperatures, characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field. The electrical resistivity of a metallic conductor decreases gradually as the temperature is lowered. However, in ordinary conductors such as copper and silver, impurities and other defects impose a lower limit. Even near absolute zero a real sample of copper shows a non-zero resistance. The resistance of a superconductor, on the other hand, drops abruptly to zero when the material is cooled below its "critical temperature". An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.
• Name three ways to check stability:
routh-herwitz criteria, nyquist criteria, root locus method
• Examples of Semiconductors, Passive devices in day to day living
Inductors used in Fans, Resitors-Passive components used in Tube lights etc
• Decribe Zener Breakdown
In Zener breakdown the electrostatic attraction between the negative electrons and a large positive voltage is so great that it pulls electrons out of their covalent bonds and away from their parent atoms. ie Electrons are transferred from the valence to the conduction band. In this situation the current can still be limited by the limited number of free electrons produced by the applied voltage so it is possible to cause Zener breakdown without damaging the semiconductor.
• Which semiconductor device is used as a voltage regulator and why?
Zener diode in reverse bias is used as voltage regulators. It allows a negligible variation in voltage for a large variation in current
• What do you mean by zener breakdown and avalanche breakdown?
There are two stages that occur as a material begins to breakdown due a large applied voltage. These are zener breakdown and avalanche breakdown
• What do you mean by an ideal voltage source?
An ideal voltage source is a source which allows infinite variataition in current through it without any change in o/p voltage
• Describe avalanche breakdown
Avalanche breakdown occurs when the applied voltage is so large that electrons that are pulled from their covalent bonds are accelerated to great velocities. These electrons collide with the others and knock off more electrons. These electrons are then also accelerated and subsequently collide with other atoms. The current in the semiconductor rapidly increases and the material can quickly be destroyed.
• Does Zener breakdown damages the device.
In the case of Zener breakdown- the current can still be limited by the limited number of free electrons produced by the applied voltage. So it is possible to cause Zener breakdown without damaging the semiconductor
