Zener Diode (ZD): Symbol A breakdown diode Basically a p-n junction with little inc. in cloping level (1:105) → Generally designed with a normal junction.. Popularly known an Constant voltage device Major application is service as a voltage regulator → Can be used as a reference voltage device Can be used as a switch (Paster than a normal drode because of higherr doping conc.) Fabricated only with the Si Always operated under reverse bias Zener diode, will be working voltage regulator circuit when operated under reverse biar When forward blow it will be working as a normal cliode Cut in voltage Can be used as a clipper. → can be used to convert the given into square wave. sine wave → The principle of zenere diode is tunnelling effect or tunnelling of charge carriers across the junction. → zenex diode when designed with abrupt. junction have and operated under reverse bias will narrow depletion layere and the clavice, will exhibit tunnelling offect zener diode ros specified in terms of break down voltage and max. power dissipation VBY 10V Prax = 400mw Zener diode are commericially available with breakdown voltage in the range of 2.51 to 3001 V-I Characteristics of zener diocle:- Izk Zener knee current or min. Iz entert Corduction If (MA) Non conducting Conducting, -VBY 0.7v + Va FB When zener diode is reverse bias below the current is practically o non-conducting and it is now breakdown volterge Zener diode ius non working When a normal cliode Reverse voltage = breakdown voltage, the Inc. to Izk and this is due to breakdown phenomenon and now zener cliode will be enter into the conduction- When reverse voltage is greater than break clown voltage t more and more current will be passing into the zener diode, the voltage drop across the device will be maintain almost as consteunt and is equal to around the break. down voltage of the device. 1 current passing through the zener cliode suddenly V-I. Characteristics of zenere cliode! In ideal zener diode when reverse voltage > breakdown voltage, the zenere cliode will be Conall cting with larger clitorend but voltage across it exactly equal to breakalou voltage of the device Synamic resistance of zener diode! - → Internal resistance of zener diode. For ideal zener aliode, dynamic resistance Equivalent circuit of zener diode: - (a) when Zener diode is forward biased!... 7 Vz. Lor VBY When zener diode is forward bias be replaced by cut in voltage. it can (b) When zener diode los reverse biased... Practical z Zener breakdown phenomenon. 18612x16 V/cm → It is due to langer electrice field intensity It is due to touring off or ruptwing of Covalent bonds within the depletion layer Zener break clown occwes for breakdowri voltage below 6٧٠٠ zener breakdown voltage dec with the temperature (NTC) The temperature coefficient of breakdown voltage iss -ve. zener