about LED/photodiode/diodes?

[Phantom-II]

Hi

so in class we've just finished electronics and photonics; i can understand most of the calculation/modulation questions, since its similar to maths but i dont quite understand the idea of a voltage drop across the diode. I was taught that they allow current to flow one way and have no resistance, but how does it effect the voltage?

[Shashim]

It has what's called a threshold voltage. It just means, as long as it is connected forward bias (correctly allowing current to flow), it will take voltage that is equal to the threshold voltage no matter how big the battery source is. But if it is connected reverse bias, there will be no current flow and it will actually consume all the voltage.


I'm not sure if I explained that well. Ask questions if u have any. Thanx.

[Phantom-II]

It's clearer now, would the presence of a threshold voltage be related to the fact that diodes conduct by creating depletion zones, which is limited in conduction?