Best 3 Applications Involving in Zener Diode Working Functionality

Best 3 Applications Involving in Zener Diode Working Functionality Introduction  Zener diodes are normal PN junction diodes operating in a reverse biased condition. Working of the Zener diode is similar to a PN junction diode in forward biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its threshold / breakdown voltage. These are among the basic types of diodes used frequently, apart from the normal diodes.Working of the Zener diode

Best 3 Applications Involving in Zener Diode Working Functionality Zener Diode Working

Best 3 Applications Involving in Zener Diode Working Functionality Semiconductor Diode in Reverse Bias Condition  PN junction diode is formed by a combination of a p type semiconductor material with an n type semiconductor material.  When one side of a semiconductor crystal is doped with donor impurities.  The other side with acceptor impurities, a PN junction is formed.

Best 3 Applications Involving in Zener Diode Working Functionality Unbiased Semiconductor Diode  The holes from the p side tend to diffuse to a low concentration region.  The same thing happens for electrons from n-side.  Thus the holes diffuse to the n-side and the electrons diffuse to the p-side.  This results in accumulation of charges around the junction, forming a depletion region.  An electric polarity or electric dipole is formed across the junction, causing flow of flux from n side to p side.

Best 3 Applications Involving in Zener Diode Working Functionality  This results in varying negative electric field intensity, generating an electric potential across the junction.  This electric potential is actually the threshold voltage of the diode.  A normal diode is biased such that a negative voltage is applied to the n side and positive voltage to the p side.  The diode is said to be in forward biasing condition. Unbiased Semiconductor Diode

Best 3 Applications Involving in Zener Diode Working Functionality Unbiased Semiconductor Diode

Best 3 Applications Involving in Zener Diode Working Functionality  Applied voltage tends to decrease the potential barrier after it goes beyond the threshold voltage.  The majority carriers cross the potential barrier and the device starts conducting with flow of current through it.  When the diode is biased in reverse condition to above, the applied voltage.  It adds to the potential barrier and hinders the flow of majority carriers.  It allow the flow of minority carriers (holes in n type and electrons in p type). Unbiased Semiconductor Diode

Best 3 Applications Involving in Zener Diode Working Functionality  As this reverse bias voltage increases, the reverse current tends to increase gradually.  At a certain point, this voltage is such that it causes breakdown of the depletion region.  Causing a massive increase in the flow of current.  This is where the zener diode working comes into play. Unbiased Semiconductor Diode

 The Working Principle of zener diode lies in the cause of breakdown for a diode in reverse biased condition. Normally there are two types of breakdown. Zener Breakdown Avalanche Breakdown. Principle Behind Zener Diode Working

Principle Behind Zener Diode Working Zener Breakdown  This type of breakdown occurs for a reverse bias voltage between 2 to 8V.  Even at low voltage, the electric field intensity is strong enough to exert a force.  The valence electrons of the atom such that they are separated from the nuclei.  This type of break down occurs normally for highly doped diode with low breakdown voltage and larger electric field.  As temperature increases, the valence electrons gain more energy to disrupt from the covalent bond and the less amount of external voltage is required.  Thus zener breakdown voltage decreases with temperature.

Principle Behind Zener Diode Working Avalanche Breakdown  This type of breakdown occurs at the reverse bias voltage above 8V and higher.  It occurs for lightly doped diode with large breakdown voltage.  As minority charge carriers (electrons) flow across the device.  They tend to collide with the electrons in the covalent bond and cause the covalent bond to disrupt.

Principle Behind Zener Diode Working Avalanche Breakdown  As voltage increases, the kinetic energy (velocity) of the electrons also increases.  The covalent bonds are more easily disrupted, causing an increase in electron hole pairs.  The avalanche breakdown voltage increases with temperature.

Best 3 Applications Involving in Zener Diode Working Functionality The 3 Zener Diode Applications 1. Zener Diode as a voltage 2. Zener Diode as a voltage reference 3. Zener Diode as a voltage clamper

The 3 Zener Diode Applications Zener Diode as a voltage  In a DC circuit, Zener diode can be used as a voltage regulator or to provide voltage reference.  The main use of zener diode lies in the fact that the voltage across a Zener diode remains constant for a larger change in current.  This makes it possible to use a Zener diode as a constant voltage device or a voltage regulator.  In any power supply circuit, a regulator is used to provide a constant output (load) voltage.

The 3 Zener Diode Applications Zener Diode as a voltage  Irrespective of variation in input voltage or variation in load current.  The variation in input voltage is called line regulation.  The variation in load current is called load regulation.

The 3 Zener Diode Applications Zener Diode as a voltage  While designing a voltage regulator using zener diode  The latter is chosen with respect to its maximum power rating.  The maximum current through the device should be:-  Imax = Power/Zener Voltage  Since the input voltage and the required output voltage is known.  It is easier to choose a zener diode with a voltage approximately equal to the load voltage, i.e. Vz ~=Vo.

The 3 Zener Diode Applications Zener Diode as a voltage  The value of the series resistor is chosen to be  R =(Vin – Vz)/(Izmin + IL), where IL = Load Voltage/Load resistance.  It is advisable to use a forward biased diode in series with the Zener diode.  This is because the Zener diode at higher voltage follows the avalanche breakdown principle, having a positive temperature of coefficient.  Hence a negative temperature coefficient diode is used for compensation.

The 3 Zener Diode Applications Zener Diode as a Voltage Reference  In power supplies and many other circuits, Zener diode finds its application as a constant voltage provider or a voltage reference.  The only conditions are that the input voltage should be greater than zener voltage.  The series resistor should have a minimum value such that the maximum current flows through the device.

The 3 Zener Diode Applications Zener Diode as a Voltage Clamper  A Zener diode can be used in a circuit involving AC input source, different from the normal PN diode clamping circuit.  The diode can be used to limit the peak of the output voltage to zener voltage.  At one side and to about 0V at other side of the sinusoidal waveform.

The 3 Zener Diode Applications  From the image, during positive half cycle, once the input voltage is such that the zener diode is reverse biased.  The output voltage is constant for a certain amount of time till the voltage starts decreasing.  During the negative half cycle, the zener diode is in forward biased connection.  As the negative voltage increases till forward threshold voltage. Zener Diode as a Voltage Clamper

The 3 Zener Diode Applications Zener Diode as a Voltage Clamper  The diode starts conducting and the negative side of the output voltage is limited to the threshold voltage.  To get an output voltage in positive range only, use two oppositely biased Zener diodes in series.

Working Applications of Zener Diode  Another application involves use of Zener diode as a voltage regulator.  Here the AC voltage is rectified by the diode D1 and filtered by the capacitor.  This filtered DC voltage is regulated by the diode to provide a constant reference voltage of 15V.  This regulated DC voltage is used to drive the control circuit.  It used to control the switching of light, as in an automated lighting control system. Working application of zener diode involving a Bluetooth device

Working Applications of Zener Diode Working application of zener diode involving a Bluetooth device

Working Applications of Zener Diode Zener Diode Voltage Regulation Application  Another application involves use of Zener diode as a voltage regulator.  Here the AC voltage is rectified by the diode D1 and filtered by the capacitor.  This filtered DC voltage is regulated by the diode to provide a constant reference voltage of 15V.  This regulated DC voltage is used to drive the control circuit.  It used to control the switching of light, as in an automated lighting control system.

Working Applications of Zener Diode Zener Diode Voltage Regulation Application