What is Zener diodes and its function?

Zener diodes are specially constructed to have accurate and stable reverse breakdown voltage. 

When it is forward biased, it behaves as a normal diode. When reverse biased, a small leakage current flows. If the reverse voltage across Zener diode is increased, a value of voltage is reached at which reverse breakdown occurs. This is indicated by a sudden increase of Zener current show in Fig. Below. The voltage after reverse breakdown remains practically constant over a wide range of Zener current. This makes it suitable for use as a voltage regulator to furnish constant voltage from a source whose voltage may vary noticeably. 

For the operation of Zener diode as a voltage regulator, (i) it must be reverse biased with a voltage greater than its breakdown, or Zener, voltage and (ii) a series resistor R, Fig.(c) is necessary to limit the reverse current through the diode below its rated value. 

where ,

• R = Load Resistance 
•  V_z = Voltage across zener diode 
•  I_z = Current across zener diode 
•  I_s = Source current 
•  I_o = Load,or output,current
•   I_s=(V_s-V_z)/R_s 
•  I_o=V_z/R 
•  I_z=I_s-I_o 
•  power rating = V_z.I_z 

These are available in a voltage range from few volts to about 280 V.

Introduction:

A zener diode is a type of diode that operates in the reverse breakdown region, making it useful for regulating voltage levels in electronic circuits. Invented by Clarence Zener in 1934, zener diodes are commonly used in power supplies, voltage regulators, and voltage reference circuits. This article will provide a detailed explanation of zener diodes, their characteristics, applications, and how to use them in electronic circuits.

 

What is a Zener Diode?

A zener diode is a type of semiconductor diode that allows current to flow in the reverse direction when a certain voltage level is reached, called the breakdown voltage or zener voltage. When the voltage across the diode is below the breakdown voltage, the zener diode operates like a regular diode, allowing current to flow in the forward direction and blocking current in the reverse direction. However, when the voltage across the diode exceeds the breakdown voltage, the zener diode begins to conduct in the reverse direction, allowing current to flow through the diode and limiting the voltage to the breakdown voltage level.

Zener Diode Symbol:

The symbol show in fig(a) for a zener diode is similar to a regular diode, but with a diagonal line through the arrowhead pointing towards the anode, indicating the reverse breakdown direction. The zener voltage or breakdown voltage is typically indicated next to the symbol, such as "5.1V" or "12V".

Zener Diode Characteristics:

The characteristic of a zener diode is show in fig(b) its breakdown voltage or zener voltage, which is the voltage level at which the diode begins to conduct in the reverse direction. Zener diodes are typically available in a wide range of breakdown voltages, from a few volts to several hundred volts, making them useful for a variety of applications. The zener voltage is typically specified with a tolerance, such as +/-5%, which indicates the range of voltage values that the diode can operate within.

Another important characteristic of zener diodes is their power rating, which is the maximum power that the diode can dissipate without being damaged. This is typically specified in watts, and depends on the physical size of the diode and the thermal properties of the package. It is important to choose a zener diode with a power rating that is appropriate for the application to avoid damage to the diode or the circuit.The main function of a Zener diode is to regulate voltage by acting as a voltage reference device. When connected in reverse-bias mode, it conducts current when the voltage across its terminals exceeds a certain threshold value known as the "Zener voltage" or "breakdown voltage".

Zener Diode Applications:

zener diodes are commonly used as electronic circuits for voltage regulation, voltage reference, and overvoltage protection. Some of the most common applications of zener diodes include:

• Voltage Regulation:Zener diodes can be used to regulate voltage levels in electronic circuits by limiting the voltage to a specific value. This is useful in applications where a stable voltage is required, such as in power supplies or voltage regulators. By placing a zener diode in parallel with the load, the voltage across the load can be limited to the zener voltage, even if the input voltage fluctuates.
• Voltage Reference:Zener diodes can also be used as voltage references in electronic circuits. By choosing a zener diode with a specific breakdown voltage, the circuit can be designed to produce a stable output voltage regardless of changes in input voltage or temperature. This is useful in applications such as analog-to-digital converters, where a stable reference voltage is required.
• Overvoltage Protection:Zener diodes can also be used to protect electronic circuits from overvoltage conditions, such as voltage spikes or transients. By placing a zener diode in parallel with the load, the voltage across the load can be limited to the zener voltage, preventing the voltage from exceeding a certain level and damaging the circuit.
• Waveform clipping: Zener diodes can be used to clip the amplitude of a waveform by limiting the  voltage swing.

Freewheeling Diodes: Basics & Applications

Q:why zener diodes are provided in dc supply?

Ans:zener diodes in dc power supplies are used for providing a reference voltage used for comparison.