voltage across zener diode is constant even if we change current across it .if current is doubled then voltage is same as earlier . please explain reason in physical way
Because you are most likely in a voltage region above the breakdown limit of your Zener diode (check it in your datasheet). If this is the case you get a kind of avalange breakdown, which means that chaning the voltage just a bit can enhance the current tremendously (up to some orders of magnitude).
On the other hand, you could say that above that limit the current can change some orders of magnitude without altering the voltage much (it is not exactly constant, but the change is so small, that it is not really measureable in some cases).
From a physical point of view you might say that the Zener diode has a junction with a high number of dopants - those can deliver a large amount of charge carriers if the breakdown voltage is sufficiently high. Hence large currents are possible.
but if voltage is decreasing a bit then current should decrease very large or not .please explain
As I said, if you are above the breakdown voltage, the voltage will decrease only very little compared to the current - however, the current will go down substentially when you decrease your voltage below the breakdown.
thank you very much , i have put another question regarding temperature coefficient of zener breakdown please explain.
Cathode voltage across discharge is constant irrelivant of current and is defined by the ionization potential of gas atoms.
- Badges
- Science topic
- Similar topics
- Philosophy
- Philosophy Of Science
- Reasoning