What is Zener Diode?
We know about the employment of Zener Diode which is to allow the current stream in forwarding or invert course. Zener Diode is a semiconductor gadget consisting of a P-N intersection that leads the current in a switch course when a specifically determined voltage is reached.
It has a converse breakdown voltage which implies it can constantly work in an opposite predisposition mode without getting harmed. A Zener Diode does not just permit current to move from anode to cathode yet in addition, in the opposite bearing on arriving at the Zener voltage. Because of this usefulness, Zener Diodes are the most generally utilized semiconductor diodes.
In the device, a reverse-biased, strongly doped p-n junction diode operating in the breakdown region is utilized. In the breakdown zone, conventional diodes and rectifiers are never used, but the Zener diode can be safely employed at the designated point.
It has a reverse breakdown voltage, which implies it can function in an opposite tendency condition for an unlimited period without being destroyed.
To obtain the Zener voltage, a Zener Diode permits the current to flow not only from anode to cathode but also in the opposite direction. Due to their versatility, Zener diodes are the most commonly used semiconductor diodes.
Zener Diode - Functions and Applications
When in forward-bias mode, the Zener diode works just like a regular diode, with a turn-on voltage of between 0.3 and 0.7 V. In any case, when converse one-sided voltage is applied to the Zener diode, it works in various ways.
A little leakage current may flow in the reverse mode.
A current begins to flow through the diode when the reverse voltage reaches the predetermined breakdown value (Vz). Now, a little expansion in invert voltage will quickly expand the electric flow. On account of this abrupt ascent in electric flow, a breakdown happens called Zener breakdown. Nonetheless, Zener Diode displays a controlled breakdown that harms the gadget.
After reaching a maximum point defined by the series resistor, the current stabilizes. It remains constant throughout a wide range of applied voltage.
At the point when opposite one-sided voltage is applied to a Zener Diode, it permits just a modest quantity of spillage current until the voltage is not exactly Zener voltage. At the point when the converse one-sided voltage applied to the Zener diode comes to Zener voltage, it begins permitting an enormous measure of electric flow.
Zener Breakdown
The Zener breakdown effect, which occurs below 5.5 V, or impact ionization, which occurs above 5.5 V, causes the breakdown. The same behavior can be obtained by both processes. They also do not necessitate any additional circuitry. However, the temperature coefficient of each mechanism is different
The temperature coefficient of the Zener effect is negative, whereas the temperature coefficient of the impact effect is positive.
At 5.5 V, the two temperature effects are nearly equivalent and cancel one other out. It makes 5.5 V Zener diodes the most stable over a wide variety of temperature settings.
Applications
Zener Diode is a Voltage Controller: At the point when the heap voltage approaches the breakdown voltage, the resistors which are associated in arrangement restrict the current through the diode when there is an abundance measure of voltage while the diode is leading.
While doing that the diode produces some sort of commotion which can be smothered by adding enormous worth decoupling capacitors across the Diode. The heap voltage rises to the breakdown voltage VZ of the Diode. The arrangement resistor restricts the current through the Diode and drops the overabundance voltage when the Diode is directed.
Overvoltage Protection
The current through the diode generates a drop across the resistor as the voltage rises to the Zener breakdown value. This results in a brief descent to the bottom.
When the information voltage exceeds the Zener breakdown voltage, current flows through the diode, causing a voltage drop across the resistor, activating the SCR, and generating a short to ground. The breaker is opened by the short out, which separates the heap from the inventory.
Switching a signal from one voltage to the next is the most common application for Zener Diodes. In breakdown regions, it can maintain a constant yield voltage. The Zener Diode is an ideal component of the activity due to its voltage-moving usage.
Zener Diode is utilized to Cut Circuits
Trimmer circuits are utilized to keep the yield signal from going past a decided incentive without transforming anything of the info signal. Employment of Zener Diode incorporates adjusting and moulding the AC waveform cutting circuits. The section circuits restrict one piece of the AC waveform to shape the waveform or give security.
These sorts of circuits are by and large utilized in TV and FM transmitters for eliminating obstruction. Zener Diodes are utilized to alter or shape AC waveform cutting circuits. The cut-out circuit cutoff points or clasps off pieces of either of the half patterns of an AC waveform to shape the waveform or give insurance.
FAQs on Uses of Zener Diode
1. What is a Zener diode and how is it different from a standard p-n junction diode?
A Zener diode is a special type of semiconductor diode specifically designed to operate reliably in the reverse breakdown region. The key difference from a normal diode is its heavy doping. This allows it to handle a controlled, non-destructive breakdown and maintain a constant voltage across it, whereas a normal diode would be permanently damaged if its reverse breakdown voltage is exceeded.
2. What are the main uses of a Zener diode in electronic circuits?
The main uses of a Zener diode stem from its ability to maintain a constant voltage. Key applications include:
- Voltage Regulation: Its primary use is to provide a stable output voltage from a varying input voltage.
- Over-Voltage Protection: It is used in circuits to protect sensitive components from voltage surges.
- Waveform Clipping: It can be used to clip or limit parts of an AC signal to a specific voltage level.
- Voltage Reference: It provides a stable and accurate reference voltage for power supplies and other circuits.
3. What is meant by 'Zener breakdown' in a Zener diode?
Zener breakdown is a type of electrical breakdown that occurs in a heavily doped p-n junction under reverse bias. Due to the high doping, the depletion region is very narrow. The intense electric field across this narrow region becomes strong enough to pull electrons directly from their covalent bonds, creating a large flow of reverse current. This process happens at a specific, predictable voltage called the Zener voltage (Vz).
4. How does a Zener diode function as a voltage regulator?
To act as a voltage regulator, a Zener diode is connected in reverse bias, parallel to the load. A series resistor limits the total current. When the input voltage increases, the excess voltage is dropped across the series resistor, causing more current to flow through the Zener diode but keeping the voltage across the load constant at the diode's Zener voltage (Vz). This ensures the load receives a stable, regulated voltage.
5. What are the key V-I characteristics of a Zener diode?
The V-I (Voltage-Current) characteristics of a Zener diode show its behaviour under different biasing conditions:
- Forward Bias: It behaves like a normal diode. Current flows easily once the forward voltage exceeds the cut-in voltage (approx. 0.7V).
- Reverse Bias: It allows only a tiny leakage current until the reverse voltage reaches the Zener voltage (Vz). At this point, a breakdown occurs, and the reverse current increases sharply with almost no change in voltage across the diode. This sharp, vertical section of the V-I curve is its primary operating region.
6. Why is a Zener diode's heavy doping crucial for its function?
The heavy doping is a critical design feature because it creates an extremely thin depletion region. This narrow barrier is essential for the Zener breakdown mechanism to occur at a precise and relatively low reverse voltage. In a regular diode with lighter doping, the depletion region is wider, and breakdown (typically Avalanche breakdown) occurs at a much higher, often destructive, voltage.
7. Besides regulation, how is a Zener diode used for waveform clipping?
In clipping circuits, a Zener diode is used to limit or 'clip' the voltage of a signal to a certain level. For example, if two Zener diodes are connected back-to-back, they can clip both the positive and negative halves of an AC waveform. This application is useful in signal processing and for protecting circuits by ensuring the signal amplitude does not exceed the Zener voltage.
8. How do Zener diodes contribute to the functioning of everyday devices like phone chargers?
In devices like phone chargers and power adapters, Zener diodes are often used to create a stable reference voltage. The main power controller in the charger compares the actual output voltage to this precise reference voltage. It then adjusts its operation to ensure the final output remains constant (e.g., at 5V), thus providing a safe and stable charge to the device's battery.
