Diode Action   

 
The diode is the most common and easiest semiconductor to understand.
DIODES normally allow current to flow only in one direction.
Zener diodes and solar cells are the exceptions and normally operate in reverse.
Diode are used in many applications the most important and common is in circuits that change AC to DC or rectifier circuits found in power supplies and battery charges. Most of our electronic appliances have a power supply that conditions the 120VAC at the mains. The  characteristic  curve  of a  DIODE below  shows the forward (positive voltage) bias and reverse (negative voltage) bias operating characteristics.


Main points:

1) after 0.7 volts are applied in the forward direction current begins to flow this is called the forward voltage



2) Zener diodes have predictable and useful reverse breakdown voltages that are used to regulate the output of some fixed voltage output power supplies.
- the Zener is placed backwards in the output of a power supply in series with a ballast resistor and the final output (load)  is in parallel with the Zener

3) the 1N prefix tells you it is a diode

4) all diodes, like most electronic components, have voltage and power ratings that must be observed in practice.

***Overloading a diode will melt it, over voltage will damage the junction***

              Characteristic Curve of a Diode

 

 

 

Forward and Reverse Bias Phenomena

 

Zener diodes - use predictable reverse breakdown voltages to regulate power supplies at the output ...... loads connected in parallel with the Zener have their voltage supply "clamped" at no higher than the reverse voltage of the Zener diode.

- a resistor must be place in series with the Zener to limit the amount of current that flows thought the diode, and can be calculated using the 
ZENER CALCULATOR.