In forward bias mode P-type of semiconductor is connected to positive terminal and Ntype of semiconductor is connected to negative terminal of battery. As voltage increases current starts flowing through diode. When the voltage applied across PN junction reaches to 0.7V (Si) the current flows through the diode i.e. the diode start conducting current as shown above. In reverse bias mode P-type of semiconductor is connected to negative terminal and Ntype of semiconductor is connected to positive terminal of battery. In this current produced is due to minority charge carriers. This current is called leakage current. As the reverse biased voltage is increased at a critical voltage VBR , the reverse current through the diode increases sharply. Most of the diodes have breakdown voltage more than 50 V.