Zener Diode

NCERT explains that a Zener diode is specially fabricated with heavy doping so that it has a sharp, well-defined breakdown voltage in reverse bias. When operated in reverse bias beyond this Zener voltage, the diode maintains an almost constant voltage across itself even as the current through it varies widely, which is the property exploited for voltage regulation. It is therefore connected in reverse bias across the load, operating in its breakdown region, so that the load voltage stays clamped at the Zener voltage. The option describing forward bias below the knee is wrong because in forward bias a Zener behaves like an ordinary diode and cannot regulate. The option placing it in series and forward biased is wrong because a Zener regulator is connected in parallel with the load, not in series with it. The option omitting a series resistor is wrong because a current-limiting resistor is essential to absorb excess voltage and prevent the Zener from being destroyed. As stated in NCERT Class 12, Chapter 14, the Zener operates in reverse breakdown for regulation. A consistency check confirms that the near-vertical breakdown characteristic keeps voltage steady while current adjusts.