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The Zener Diode

April 29, 2019

Zener Diode:

The Zener diode behaves similar to a traditional general diode consisting of an element PN junction and once biased within the forward direction, that’s Anode positive with relevancy its Cathode, it behaves similar to a traditional signal diode passing the rated current. “A junction rectifier blocks current within the reverse direction, however, can suffer from premature breakdown or injury if the reverse voltage applied across becomes too high.”

This is as a result of once the reverse voltage applied across the Zener diode exceeds the rated voltage of the device a method referred to as Avalanche Breakdown happens within the semiconductor depletion layer and a current starts to flow through the diode to limit this increase in voltage. However, the Zener Diode or “Breakdown Diode”, as they’re generally referred too, is essentially an equivalent because the commonplace PN junction diode however they’re specially designed to possess a coffee and given Reverse Breakdown Voltage that takes advantage of any reverse voltage applied thereto.

The point at that the Zener voltage triggers this to flow through the diode may be terribly accurately controlled (to but 1 Chronicle tolerance) within the doping stage of the diodes semiconductor construction giving the diode a selected Zener breakdown voltage, ( Vz ) for instance, 4.3V or 7.5V. This Zener breakdown voltage on the I-V curve is nearly a vertical line.

Zener Diode Voltages:

A typical Zener diode for general electronic circuits is that the 500mW, BZX55 series or the larger one.3W, BZX85 series were the Zener voltage is given as, for instance, C7V5 for a seven.5V diode giving a diode reference range of BZX55C7V5.

The 500mW series of Zener diodes area unit on the market from concerning two.4 up to concerning one hundred volts and generally have a constant sequence of values as used for the five hundred (E24) electrical device series with the individual voltage ratings for these little however terribly helpful diodes. further, as manufacturing one stable voltage output, Zener diodes may also be connected along nonparallel at the side of traditional Si signal diodes to supply a spread of various reference voltage output values as shown below.

Clipping Circuits of Zener diode:

Diode clipping ANd clamping circuits square measure circuits that square measure wont to form or modify an input AC manufacturing an otherwise shape output wave shape counting on the circuit arrangement. Diode clipper circuits are known as limiters as a result of they limit or clip-off the positive (or negative) a part of AN input AC signal. As Zener clipper circuits limit or cut-off a part of the wave shape across them, they’re chiefly used for circuit protection or in wave shape shaping circuits.

Thus far we’ve checked out however a Zener diode is wont to regulate a continuing DC supply however what if the input wasn’t steady state DC however AN alternating AC wave shape, however, would the Zener diode react to a perpetually ever-changing signal.

We needed to clip AN output wave shape at +7.5V, we’d use a seven.5V Zener diode. If the output wave shape tries to exceed the seven.5V limit, the Zener diode can “clip-off” the surplus voltage from the input manufacturing a wave shape with a flat high still keeping the output constant at +7.5V. Note that within the forward bias condition a Zener diode continues to be a diode and once the AC wave shape output goes negative below -0.7V, the Zener diode turns “ON” like every traditional semiconducting material diode would and clips the output at -0.7V

In alternative words a peak-to-peak voltage of fifteen.4 volts rather than expected fourteen volts, because the forward bias potential unit drop across the diode adds another zero.7 volt in every direction.

This type of clipper configuration is fairly common for shielding associate electronic circuit from overvoltage. the 2 Zener’s are usually placed across the ability provide input terminals and through traditional operation, one among the Zener diodes is “OFF” and therefore the diodes have very little or no have an effect on. However, if the input voltage wave shape exceeds its limit, then the Zener’s flip “ON” and clip the input to shield the circuit. In the next tutorial regarding diodes, we’ll inspect exploitation the forward biased PN junction of a diode to provide lightweight. we all know from the previous tutorials that once charge carriers move across the junction.

Zener Diode Regulator:


The load is connected in parallel with the Zener diode, therefore the voltage across RL is usually identified because of the Zener voltage, ( VR = VZ ). there’s a minimum Zener current that the stabilization of the voltage is effective and therefore the Zener current should keep higher than this worth operational underneath load among its breakdown region the least bit times. The higher limit of current is after all dependant upon the facility rating of the device. the provision voltage VS should be larger than VZ.

The electrical device, RS is connected asynchronous with the Zener diode to limit the present flow through the diode with the voltage supply, VS being connected across the mix. The stable output voltage Vout is taken from across the Zener diode. The Zener diode is connected with its cathode terminal connected to the positive rail of the DC provide thus it’s reverse biased and can be operational in its breakdown condition. electrical device RS is chosen thus to limit the utmost current flowing within the circuit.

Zener Diode Standard Zener Voltages:


I-V Characteristics of Zener Diode:

This ability to manage itself may be wont to nice impact to manage or stabilize a voltage supply against offer or load variations. the actual fact that the voltage across the diode within the breakdown region is sort of constant seems to be a very important characteristic of the Zener diode because it may be utilized in the only styles of transformer applications.

The Zener Diode is employed in its “reverse bias” or reverses breakdown mode, i.e. the anode of the diode connects to the negative offer. From the I-V characteristics curve higher than, we are able to see that the Zener diode incorporates a region in its reverse bias characteristics of just about a relentless negative voltage despite the worth of this flowing through the diode and remains nearly constant even with massive changes in current as long because the Zener diodes current remains between the breakdown current IZ(min) and therefore the most current rating IZ(max).

The perform of a regulator is a relentless output voltage to a load connected in parallel with it in spite of the ripples within the supply voltage or the variation within the load current and therefore the Zener diode can still regulate the voltage till the diodes current falls below the minimum IZ(min) worth within the reverse breakdown region.