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Will the diode operate the same way irrespective of its position?

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santom

Full Member level 2
HI all,
I just have one question.Will the diode operate the same way irrespective of its position (i.e) either in the cathode to anode direction or in the other direction.Will it have any influence in the voltage waveform?Help me if anyone knows about it..?

General doubt

I just have one answer.
NO.

General doubt

It will conduct if Forward biased and resist of revers biased!

Re: General doubt

Obviously, if you operate above nominal voltage range, at reverse polarity it behaviour is like a zenner diode, but it's not regular operation, due sometimes it fires and bocomes a short-circuit.

+++

Re: General doubt

if the diode alone is in the circuit, i think it wont be big issue. but if it is in some other circuit, it makes a big difference. can u get it?

Re: General doubt

it wont work,
that is what is called as reverse biasing of the diode.

Re: General doubt

It all depends upon the frequency of the signal and the diode capacitance. At low frequencies the forward biased diode is almost a short circuit and reversed is an open circuit.

At higher frequencies the reversed is a capacitor of high enough value to pass some of the signal.

santom

Points: 2
General doubt

A diode only conducts in one direction.In the other direction it only feebly conducts.

Re: General doubt

Do you mean in the same circuit, if you reverse the diode, will it function the same? Of course not. And it differs if your circuit voltage supply is AC or DC.

In simple words, any diode has a threshold voltage ( usually around 0.7V for Silicon diodes), so if you apply a voltage higher than that threshold voltage across the diode, in the right direction, that is from anode to cathode, the diode will simply behaves as a short circuit, or more specific, as a DC battery of 0.7V. If you apply a voltage less than the threshold, or apply the voltage from cathode to anode. the diode will simply behave as an open circuit.

So, if you are using your diode in a DC only circuit, if the voltage across the diode is high enough to make it ON (higher than threshold voltage), then if u reverse the diode, it will sure be off.
But if you are using the diode in an AC circuit, the diode will probably work in both directions. If in a case, the diode is ON, this will be probably for a part only of the cycle, the part of the voltage sine wave where the voltage exceeds the threshold, then if u reverse the diode, there will probably be another part of the sine wave in the opposite half which will exceed the threshold too, but in the opposite direction. So, may b the diode will work in both directions, but surely the output waveform will not be the same, at least reversed in direction.

I hope this helps you somehow

santom

Points: 2
Re: General doubt

Thank you very much for all of ur replies..

I think I should have been more specific in my question about the exact situation.
The circuit which I am referring to has an AC supply.
It is basically a RF receiver circuit.
It also has got a capacitance which can storethe voltage at the time when the diode is in the opposite direction to the supply voltage direction(Reverse Bias)

In normal mode ,if the diode is placed in the anode-cathode direction,the capacitor is going to store the energy in the reverse bias condn of the diode..and we get only the positive voltage waveform at the output.NO doubt in it...

What will happen if it is placed in the oppposite fashion..

(NOTE:the friend who posted finally had got my point almost I suppose.I got something clear about that now.Still,I want all of you to know about my doubt so that it will be helpful to all of us.. )

Re: General doubt

hey...

i think that the output now will be all negative....
thats 'coz , when the ac is given in the positive half the diode wont be conductin as u have kept it in the fwd bias position...but when in the neg cycle the diode conducts through it and the capacitor charges but in the opposite polarity which it would have been charged otherwise, i.e, when in the fwd bias....n as usual in the next positive cycle the capacitance may get discharged a bi 'coz of leakage n the cycle repeats...

i think this is what happens....i dont have software to simulate it n see now..but as soon as i get it ...i will post u back...

General doubt

no but if reverse voltage is rising to brakdown voltage diode burns.

General doubt

in ac ,cathod/anode doesn't make any sense but in dc ,does matter.

Re: General doubt

If by changing the diode does not have any effect, then simple no need for it. Anyway above explanations are right.

Regards

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