Diode is a one of the special component which can carry current only for one direction.It has two terminals which call as anode(A) and cathode(K). Early day use diode valve, but today its mainly a semiconductor device.
So diode usually called as P N Junction diode. It is widely use with electronic circuits for rectification or switching.
Diode and symbol
Anatomy of diode – Regular diode make with using P N junction.
When connecting P and N type semiconductors each, some of negatively charged electrons moves to positively charged holes, so as some positively charges holes connect with negatively charged electrons. Due to this reason it can cause inter voltage barrier gap which make reduce small voltage amount when forward biasing.As standard For germanium this is about 0.2V and for silicon about 0.7V.
Two types of biasing –
forward biasing – Only This way current can flow through diode. in here positive current also connect with semiconductor P which is positively charged, and negative current also connect with semiconductor N which is negatively charged.
So it will cause electrons and holes Repulsion each other with reverse directions and cause pass current easily. However due to internal current barrier cause small voltage drop this way.Also according to its semiconductor material type and size, each diode has its maximum forward current, voltage and frequency limits
reverse biasing – This way any current can’t flow through a diode.
That because negative also connect with semiconductor N which is negatively charged, and positive also connect with semiconductor P which is positively charged.
So each other attract each other which cause increase internal barrier farther. So now it has highest resistance so its can not carry any current.
There are several types of diodes used for electronic circuits, like Rectifier, zenar diode, crystal diode, schotkey diode, varicap etc.
Diode types-
Rectifiers – Most common diode, its used for power supply circuits for converting AC to DC.
Crystal diode – Used for demodulate radio frequency.
Zenar diode – This diode PN junction make with special way as it can work for reverse biased.So Its make for stable for certain voltage value, even if increase voltage around it.Like 6.2V Zenar diode give only 6.2v even at 9v.But this voltage cannot be too high and every zenar has maximum power(watts – W like 300mw, 1W) limit which can not exceed.Zenar diodes specially use for voltage stabilization(used with regulators).
LED – regular LED s are also diodes which make with PN junction, the deference is these are specially use some materials for emit light when connect anode and kathodes.
varicap – Use as a electronic tuning capacitor.This diode also work as reverse bias, Its specially design for change its internal field capacity as change voltage around it.So it can act as voltage control capacitor.
besides these many other diodes available.