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What is the primary function of a Zener diode in an electronic circuit?
Rectification
Voltage regulation
Signal amplification
Oscillation
Voltage regulation
A Zener diode is a special type of p-n junction diode designed to operate reliably in the reverse breakdown region. Its primary function is to maintain a constant output voltage across its terminals despite fluctuations in the input supply voltage or load current.
A Zener diode is a special type of p-n junction diode designed to operate reliably in the reverse breakdown region. Its primary function is to maintain a constant output voltage across its terminals despite fluctuations in the input supply voltage or load current.
Think of a Zener diode like a pressure relief valve on a steam engine; no matter how high the steam pressure gets, the valve opens to bleed off the excess, keeping the system pressure steady at a safe, fixed limit.
Zener = Zero change (in voltage).
VoutтАЛ=VZтАЛ тАФ The output voltage remains clamped to the Zener breakdown voltage.
IZтАЛ=RsтАЛVinтАЛтИТVZтАЛтАЛ тАФ The Zener current calculated using the series resistance RsтАЛ.
When reverse-biased beyond the Zener breakdown voltage (VZтАЛ), the Zener diode exhibits a sharp decrease in resistance, allowing current to flow while keeping the voltage across it nearly constant. This is achieved through either Zener breakdown (quantum tunneling) in heavily doped diodes or avalanche breakdown in lightly doped ones. Because the voltage drop remains stable once VZтАЛ is reached, it effectively 'clamps' the output voltage.
Zener diodes are always connected in reverse bias for regulation purposes.
They are heavily doped compared to standard signal diodes to allow for the Zener effect.
The breakdown region in a Zener diode is non-destructive, provided the power dissipation limit is not exceeded.
Provides a very stable reference voltage
Compact size and solid-state reliability
Low cost and easily available
Limited power handling capacity
Output voltage can vary slightly with temperature changes
Voltage regulators in power supplies
Overvoltage protection circuits (crowbar circuits)
The Zener breakdown voltage typically ranges from 2V to 200V depending on doping concentrations.
Option A (Rectification) is the function of a standard PN junction diode.
Option C (Signal amplification) is the function of a transistor (BJT/FET).
Option D (Oscillation) is the function of an LC circuit combined with an active element like a transistor or Op-Amp.
B is correct тАФ The Zener diode is specifically designed to operate in the reverse breakdown region to provide a stable reference voltage, acting as a voltage regulator.
In competitive exams, remember that standard diodes are used for rectification (forward bias), while Zener diodes are used for regulation (reverse bias).