Diode is a semiconductor device made up by cascading P-type semiconductor and N-type Semiconductor. The cascading of P-type semiconductor part and N-type semiconductor part leads to form a junction between them . The charges at junction neutralize each other and forms depletion layer.
Such a semiconductor junction restricts the flow of current in one direction , this leads to polarity sensitive nature.
A diode can be operated in two modes.
- Forward Bias .
- Reverse Bias .
Forward Bias :
The positive terminal of battery is connected to positive terminal of the diode and negative terminal of the battery is connected to negative terminal of the diode .
Reverse Bias :
The positive terminal of battery is connected to negative terminal of the diode and negative terminal of the battery is connected to positive terminal of the diode .
The current flows when the diode is in forward bias and the applied voltage must greater than cut-in voltage of diode. The cut-in voltage for germanium made devices is 0.3V and for silicon made devices is 0.7V . In ideal conditions there is no current flows in reverse bias . In normal conditions of reverse bias a small amount of current flows , it is called as reverse leakage current . This reverse current is independent of applied voltage across the diode in reverse bias .
In reverse bias mode ,if the biasing voltage is more that a particular range the junction in the diode will break which leads to sudden increase in current and damage of diode which is called as Breakdown Voltage .
Equivalent Circuit of Diode :
Vr = Voltage across Juncton .
R = Resistance offered by diode .
V-I Characteristics of diode :
V-I Characteristics of diode is expressed by the universal diode equation given by ;
For remaining topics of diode move to basic electronics content page
- What is Diode
- Specifications of Diode
- Bias Modes
- Package Styles
Link to move content page Basic Electronics