Basic Operations and Applications of Zener Diode

Zener diode is one of the types of diodes which works similar to a PN junction diode. The only difference is that Zener diode works in reverse biased condition. Also, if a PN junction diode is connected in reverse biased condition, it cannot be used as Zener diode. Therefore, what is Zener diode?

Zener diode is defined as a semiconductor device that allows current to flow either in reverse or forward direction.

Operation of Zener diode

The working of the Zener diode is similar to any normal diode with the working voltage of 0.3 and 0.7 V. When the Zener diode is connected in reverse mode, there is a small leakage current that flows.

There are a few specifications that are related to the Zener diode and they are as follows:

• Voltage Vz is the reverse breakdown voltage of the Zener diode and may range from 2.4V to 200V. The maximum voltage may go up to 200V.
• Current Iz_max is the maximum current that ranges between 200μA to 200A.
• Current Iz_min is the minimum current that ranges between 5mA and 10mA.
• The voltage tolerance of a Zener diode is ±5%.
• These diodes have temperature stability of 5V.

Advantages of Zener diode

• Less expensive
• Compact size
• High power dissipation capacity
• Accuracy is high

Applications of Zener diode

• Zener diode is used as a voltage regulator.
• Clipping and clamping circuits use Zener diodes.
• Zener diodes find applications as shunt regulators.

Example on Zener diode

A 5.0V stabilized power supply is needed, which is produced from a 10V DC power supply input source. P_z, the maximum power rating of the Zener diode is 3W. Calculate the maximum current flowing, the minimum value of the resistors in series, load current, and Zener current.

Solution:

The maximum current that flows through the Zener diode is given as:

Maximum current, Iz_max= (Watts)/(Voltage) = (3W)/(5V) = 600mA

The minimum value of the resistors in series is given as:

R_s = (V_s - V_z)/Iz_max = (10-5)/600 = 83.3Ω

The load current is calculated by considering the resistor to be of 1kΩ and is given as:

I_L = V_z/R_L = (5)/(1000) = 5mA

The Zener current I_z is given as:

I_z = Iz_max - I_L = 600 - 5 = 595mA.

Interested to learn more about other types of diodes such as Schottky diode, stay tuned with BYJU’S.