Uses of zener diode, Electrical Engineering

Uses of Zener Diode

Zener diodes are extensively used as voltage references and like shunt regulators to regulate the voltage across small circuits. While connected in parallel with a variable voltage source so that it is reverse biased, a Zener diode conducts while the voltage arrives at the diode's reverse breakdown voltage. From that point on, the comparatively low impedance of the diode holds the voltage across the diode at that value.

402_Uses of Zener Diode 2.png

 In this type of circuit, a typical voltage reference or regulator, an input voltage that is denoted by UIN, is regulated down to a stable output voltage that is denoted by UOUT. The intrinsic voltage drop of diode D is stable over a broad current range and holds UOUT comparatively constant even though the input voltage might fluctuate over a fairly wide range. Due to the low impedance of the diode while operated like this, Resistor R is employed to limit current through the circuit.

180_Uses of Zener Diode 1.png

 Figure: Zener diode shown with typical packages. Reverse current - iZ is shown.

In the case of this general reference, the current flowing in the diode is determined by using Ohms law and the known voltage drop across the resistor R. IDiode = (UIN - UOUT) / RΩ

The value of R has to be satisfies two conditions:

1. R must be enough small that the current via D keeps D in reverse breakdown. The value of this current is provided in the data sheet for D. For instance, the common BZX79C5V6 device, a 5.6 V 0.5 W Zener diode, has a suggested reverse current of 5 mA. If insufficient current exists by D, then UOUT will be not regulated, and less than the nominal breakdown voltage (this varies to voltage regulator tubes in which the output voltage will be higher as compared to the nominal and could rise as high as UIN). While measuring R, allowance must be made for any current via the external load, not displayed in this diagram, connected across UOUT.

2. R must be sufficiently large that the current via D does not destroy the device. If the current through D is ID, the breakdown voltage VB of it and the maximum power of it dissipation PMAX, then IDVB < PMAX.

A load might be located across the diode in this reference circuit, and as long as the zener stays in reverse breakdown, the diode will give a stable voltage source to the load.Shunt regulators are simple, but the needs that the ballast resistor be small enough to prevent excessive voltage drop throughout worst-case operation (low input voltage concurrent with high load current) tends to leave numerous current flowing in the diode much of the time, making for a quite wasteful regulator with high quiescent power dissipation, only appropriate for smaller loads.

Zener diodes in this type of configuration are frequently employed as stable references for much more advanced voltage regulator circuits.These devices are as well encountered, usually in series with a base-emitter junction, in transistor stages in which selective choice of a device centered around the avalanche or Zener point can be employed to introduce compensating temperature co-efficient balancing of the transistor PN junction. An instance of this type of use would be a DC error amplifier employed in a regulated power supply circuit feedback loop system.

Zener diodes are as well employed in surge protectors to limit transient voltage spikes. Other notable application of the zener diode is the make use of noise caused by its avalanche breakdown in a random number generator which never repeats.

Posted Date: 1/11/2013 12:37:25 AM | Location : United States







Related Discussions:- Uses of zener diode, Assignment Help, Ask Question on Uses of zener diode, Get Answer, Expert's Help, Uses of zener diode Discussions

Write discussion on Uses of zener diode
Your posts are moderated
Related Questions
Find Dispersion Relation for Free Electron Question: Find the dispersion relation for a free electron, and, thus, observe the relation between its rest mass and effective ma

Responses to Exponential Excitations Let us consider Aest as a typical exponential excitation in which A is a constant and s is a complex- frequency variablewith a dimension of

Q. A rectangular loop is placed in the field of an infinitely long straight conductor carrying a current of I amperes, as shown in Figure. Find an expression for the total

Q. An antenna has beam widths of 3° and 10° in orthogonal planes and has a radiation ef?ciency factor of 0.6. Find the maximum radiation inten- sity if 1 kW is applied to the anten

Q. What Are the Differences Between Enhancement And Depletion Mosfet? Depletion MOSFET:Here a slab of p_type material is formed from a silicon base and referred to as substrate

Questions: A magnetic core with a primary winding with 40 turns and a secondary winding with 80 turns has a leakage path dominated by an air gap as shown in the figure. The iro

The one line diagram of a simple three-bus power system is shown in the figure below.  Each generator is represented by an emf behind the transient reactance.  All impedances are e

Explain factors that change the resistivity of conducting materials. Temperature- Electrical resistance of most metals rises with increase of temperature whereas those of sem

Theoretical Circuit The theoretical circuit is available in form 1.Passive materials with mediocre dimension is used by the manufacturer. In order to make a theoretical circuit

Q. Show Principal source of energy? The principal source of energy comes from the burning of fossil fuels such as coal and oil to generate steam, which drives steam turbines, w