Write two important considerations used while fabricating a Zener diode. Explain, with the help of a circuit diagram, the principle and working of a Zener diode as voltage regular.
Important considerations while fabricating Zener diode are:
i) Heavily doped p and n junctions are to be used for fabricating Zener diode.
ii) The breakdown voltage of the material must be noted down to avoid destruction of the device.
Principle: A properly doped p–n junction that is supposed to work in a breakdown region is called a Zener diode. Such a junction when reverse biased shows a sudden increase in current to a high value at a certain voltage known as the breakdown voltage or the Zener voltage.
Working: A Zener diode is connected across the fluctuating voltage source through a resistance R. A constant voltage supply is maintained across the load resistance RL.
When the input voltage increases, the resistance of the Zener diode decreases and hence the current through the diode increases. Thus, a large voltage drop is seen across the resistance R and the output voltage across RL remains at a constant value. When the input voltage decreases, the resistance of the Zener diode increases and hence the current through the diode decreases. Only a small voltage drop takes place now across the resistance R and the output voltage at RL remains constant. Thus, we get a constant voltage in spite of the fluctuating input voltage. In this way, a Zener diode acts as a voltage regulator.
