Typical Power Dissipation ratings are from 150mW to 50W. Applying a reverse bias causes a strong electric field get applied across the device. Holes diffusion is from p-type to n-type and electron diffusion is from n-type to p-type. The diode consists of a special, heavily doped p-n junction, designed to conduct in the reverse direction when a certain specified voltage is reached. Physical Construction of Zener diode: In zener diode heavily doped P and N semiconductors are used, this doping intensity increased by adding impurity to the semiconductor.
The Zener diode on the other hand is specially designed to have a reduced breakdown voltage called Zener voltage. As a result of this, the width of the depletion layer increases and leads to a reduction in the capacitance of the p-n junction. When the reverse bias applies across the diode and the supply voltage is equal to the Zener voltage then it starts conducting in the reverse bias direction. The maximum reverse current is limited, however, by the wattage rating of the diode. The Zener diode produces a stable reference voltage across the load which fulfills the criteria of regulator requirement. The depletion region of the Zener diode is very thin because of the impurities.
Dark current generates in the absence of light. Zener discovered this electrical property. For the device package shown in Fig. V-I Characteristics of Zener Diode: In forward bias Zener works as an ordinary diode but when it is operated in reverse bias its shows the specialty of voltage regulation, it must be noted that in fig given below. The arrowhead on the symbol still points in the conventional direction of forward current when the device is forward biased. It can be used to introduce compensating temperature coefficient balancing of the transistor.
In a diode circuit, a diode may be connected to any of a wide variety of other electrical or electronic devices — capacitors, , transformers, power supplies, etc. Zener Diode Connectivity These devices are also encountered in series with a base emitter junction. We also carry Zener diodes with nominal working voltage up to 1 kV. This explains the zener diode characteristics in the reverse bias region. If the device becomes forward biased, then the equivalent circuit for a forward-biased diode must be used. The two temperature effects are almost equal at 5. For Wave Shaping — The Zener diode is used for converting the sine wave into the square wave.
The Zener effect has a negative temperature coefficient while the impact effect experiences a positive coefficient. A Zener Diode is a special type of diode which is designed to operate in reverse bias because it has very thin depletion region that makes this diode to handle large reverse breakdown voltage. Result: The characteristics and Voltage Regulation of Zener diode are studied. Thus, the square wave appears across the output terminal. Regular applications include providing a reference voltage for voltage regulators. The function of a regulator is to provide a constant output voltage to a load connected in parallel with it in spite of the ripples in the supply voltage or the variation in the load current and the zener diode will continue to regulate the voltage until the diodes current falls below the minimum I Z min value in the reverse breakdown region.
This is typically one to two volts higher than the rated voltage of the Zener and is known as the Zener voltage or Avalanche point. When the voltage rises beyond the Zener voltage they offer a low resistance path and large current flow through the diode. Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across circuits. What are the different types of breakdowns in semiconductor junctions? As the reverse bias increases the current increases rapidly in a direction opposite to that of the positive voltage region. When this occurs, a small change in the voltage will results in a large current flow.
Although Zener and avalanche are two different types of breakdown, the name is commonly applied to all breakdown diodes. The reverse voltages are increasing but reverse current extremely small up to Vz and remains constant till reverse voltages are reached at knee voltages the voltages at which current rapidly increasing Is known as knee voltages after the knee voltages reverse current is rapidly increasing its known as Zener current, the Zener current is the effect of Zener resistance or we can say Zener impedance which decreased when Zener current rapidly increased, above the knee Zener breakdown voltages are essentially constant. When the overload occurs across the diode most of the current pass through the diode. Read Further: Thanks for reading about zener diode… Please leave your comments below…. Note the voltage and current values carefully, after break down 6.
This type of clipper configuration is fairly common for protecting an electronic circuit from over voltage. The Zener conducts the least current when the load current is the highest and it conducts the most current when the load current is the lowest. Under the influence of the applied electric field, the valance electrons will be accelerated to knock and release other electrons. The ac equivalent circuit is used in situations where the Zener current is varied by small amounts. Symbol of Zener Diode: We can identify the terminals of zener diode by observing a black color ring at cathode terminal refer the first figure in this post. What is cause of reverse breakdown? Zener Diode Zener Diode It is mainly a special property of the diode rather than any special type of equipment. But when the reverse voltage applies across it and the reverse voltage rises beyond the predetermined rating, the Zener breakdown occurs in the diode.
For Meter Protection — The Zener diode is generally used in multimeters for controlling the movement of the meter against accidental overloads. It will regulate voltage up to its Zener voltage value. What are the applications of Zener diode? In other words a peak-to-peak voltage of 15. So for example, if we wanted to clip an output waveform between two different minimum and maximum values of say, +8V and -6V, we would simply use two differently rated zener diodes. This is known as Zener break down. By I marked over the device, we can know the value it.