Forward biasing

Reverse biasing

 (i) Positive terminal of the battery is connected to the P-crystal and negative terminal of the battery is connected to N-crystal 

 (i) Positive terminal of the battery is connected to the N-crystal and negative terminal of the battery is connected to P-crystal           

(ii) Width of depletion layer decreases

(ii) Width of depletion layer increases

(iii) R_Forward » 10Ω - 25Ω

(iii) R_Reverse » 10⁵Ω

(iv) Forward bias opposes the potential barrier and for V > V_B a forward current is set up across the junction.

(iv) Reverse bias supports the potential barrier and no current flows across the junction due to the diffusion of the majority carriers.

(A very small reverse currents may exist in the circuit due to the drifting of minority carriers across the junction)

(v) Cut-in (Knee) voltage : The voltage at which the current starts to increase. For Ge it is 0.3 V and for Si it is 0.7 V.

(v) Break down voltage: Reverse voltage at which break down of semiconductor occurs. For Ge it is 25 V and for Si it is 35 V.

 (vi)      df - diffusion ;             dr - drift

(vi)