BlogNCERTZener Diode as a Voltage Regulator

Zener Diode as a Voltage Regulator

Zener diodes are semiconductor devices that cause the current to flow in a backward or forward direction, and they tend to be heavily doped and possess a P-N junction. When a certain voltage is reached, it is specifically designed to reverse the flow of current.

In addition to having a reverse breakdown voltage, the Zener diode also has a reverse breakdown current. But what does that mean? When the diode is in reversible mode, the current conducted by it remains constant, and the voltage drop stays constant, no matter how much voltage or force is applied. Therefore, the Zener diode is thought to be extremely useful in electronic circuits when it comes to voltage regulation.

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    How is the Zener Diode Circuit Depicted?

    Zener diodes function in reverse-bias mode, as we already know. Consequently, the negative terminal of the power supply connects to the p-type material in the Zener diode, while the positive terminal is connected to the n-type material. The semiconductor material in the diode is heavily doped, which results in a thin depletion region.

    How does the Zener Diode Work?

    Thousands of impurities are added to the semiconductor material of the Zener diode to boost its conductivity. Thus, the depletion region becomes thinner. Even when a small voltage is applied to the system, the application of electric fields is intensified across this depleted region.

    What happens when the Zener diode doesn’t have to be biassed? In a p-type semiconductor, there is a valence band in which electrons are bound together. This causes zero current to flow across the semiconductor. The electrons in the valence band are referred to as valence band electrons. Electrons start moving from one valence band to another once external energy is applied.

    What does the situation look like when the Zener diode is reverse biassed? As a matter of fact, when the Zener and supply voltages are equal, the diode conducts in reverse-bias mode. Zener voltage is the voltage at which the depletion region vanishes completely when the depletion region thins out.

    An electric field intensifies when a reverse bias is applied across the diode since the depletion region has thinned out. Consequently, the electrons move from the valence band of the p-type semiconductor material to the conduction band of the n-type semiconductor material. By doing so, the barrier between the two semiconductor materials is destroyed. The diode conducts current in reverse bias direction at this voltage and current field level.

    Zener diodes consist of silicon semiconductors with a p-n junction that is specifically designed to operate in reverse bias. The diode operates as a normal signal diode when forward biased, but when a reverse bias is applied, the voltage remains constant for a wide range of currents. DC circuits use it as a voltage regulator because of this characteristic.

    Zener diodes are voltage regulators that are primarily designed to maintain a constant voltage. Let us say if a Zener voltage of 5 V is used, then the voltage becomes constant at 5 V, and it does not change.

    What is a Voltage Regulator?

    A voltage regulator regulates the level of voltage. The input voltage is essentially stepped down to the desired level and then maintained at that level throughout the output supply. When a load is applied, a voltage drop is avoided because of this. Voltage regulators are used primarily for two reasons:

    1. Changing or regulating the output voltage
    2. In spite of variations in supply voltage, to maintain the output voltage at the desired level.

    Various components of the plant are controlled by voltage regulators, such as computers, generators, and alternators.

    Zener Diode as a Voltage Regulator

    A series resistor limits the current passing through the diode by connecting it to the circuit. Normally, the positive terminal of the d.c. is connected to the pulsator. The reverse-biassed device works in such a way that it can also operate under breakdown conditions. A simple junction diode cannot be used because the diode’s low power rating could be damaged if reverse bias is applied above its breakdown voltage. The Zener diode current should always be minimum when the minimum input voltage and the maximum load current are applied.

    Since the input voltage and the required output voltage are known, it is easier to select a Zener diode with a voltage that is approximately equal to the load voltage, i.e., VZ = VL.

    The value of the series resistor is written as RS = (VL − VZ)IL

    When the voltage across the diode tends to increase, the current through the diode increases, which causes the resistance to drop in voltage. When the voltage across the diode decreases, the current through the diode also tends to decrease. The voltage drop across the resistor is very small in this case, so the output voltage is normal.

    VI Characteristics of the Zener Diode

    The Zener diode is nothing more than an ordinary diode when it is in forwarding bias mode; when the reverse bias is applied, however, the reverse voltage increases. When the reverse voltage increases, the Zener diode melts completely.

    Under these conditions, the current flow in the reverse direction, which is what is known as a breakdown voltage. As we can see from the graphs, the Zener diode possesses a considerable amount of resistance, as well as a nonlinear breakdown.

    Hence, the Zener diode’s voltage is given by the following equation – V = VZ + IZRZ

    Applications of the Zener Diode

    Zener diodes are used in industrial and commercial settings. Voltage stabilizers sustain a large amount of voltage. A constant voltage will be supplied to the power load from here since the voltage fluctuates. As a result, the Zener diode is usually connected in parallel with the load. As a result of its ability to maintain a constant voltage, it also acts as a voltage regulator or a stabilizer. A Zener diode can be used in a commercial setting.

    Industrial and commercial buildings use large power meters that are vulnerable to meter overloads. Parallel connections between these multimeters and the Zener diode, however, prevent accidental system overloads. When an overload occurs, most of the current flows through the diode, which protects the meter.

    Zener diodes are connected back to back and in opposite directions, forming a series circuit with the resistance of the circuit, which makes it possible to transform a sine wave into a square wave.

    In addition, certain specifications exist for Zener diodes, such as Zener voltage, the minimum current needed for breakdown, the maximum current, and the power that can be dissipated by the Zener diode. Zener diodes also have certain specifications regarding temperature stability and Zener resistance. A conventional electric current flows from anode to cathode in the Zener diode. A reverse bias is required to make this silicon semiconductor work. The flow of current can, however, be reversed if a specific voltage is exceeded, known as the breakdown voltage or Zener voltage. Additionally, the Zener diode is operated at reverse voltage to guarantee a constant voltage for a wide range of currents.

    Also read: Insulators

    Frequently Asked Questions

    What is the factor needed in order to keep the diode in the breakdown region?

    Voltage regulation requires a minimum amount of reverse current for the diode to remain in the breakdown region.

    How should the breakdown region be set during diode manufacturing?

    It is possible to control the breakdown region during the manufacturing of a diode by controlling the doping level.

    How does a Zener breakdown occur?

    Zener breakdown occurs when a breakdown occurs in both the rectifier and the Zener diode.

    When the input varies within limits, how does the DC output voltage fluctuate?

    In voltage regulating devices, a constant DC output voltage is obtained when the input varies within limits.

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