Classification of Materials Based on current conduction materials

Classification of Materials Based on current conduction, materials are classifieds as 1) Insulators 2) Ex: Wood, Mica, Diamond 3) 2) Conductors 4) Ex: Copper, Aluminium 5) 3) Semiconductors 6) Ex: Silicon, Germanium

Energy Bands

Semiconductors They are of two types 1) Intrinsic Semiconductors (Pure) 2) Extrinsic Semiconductors (Impure) 3) Intrinsic is doped to form Extrinsic 4) Adding Impurities is called as Doping

Depending on the impurities, there are two types of Extrinsic Semiconductors 1) n-type 2) p-type 2) N-type are formed when pentavalent impurities like arsenic are added to pure semiconductor 3) P-type are formed when trivalent impurities like gallium are added to pure semiconductor

Formation of n-type semiconductor

Formation of p-type semiconductor

p-n junction as diode

p-n junction forward biased

p-n junction reverse biased

V-I Characteristics of Diode

Diode Resistance �d. c resistance (static resistance) It is the ratio of Voltage to the current in forward biased Diode �a. c resistance (dynamic resistance) rf = ΔV/ΔI �Reverse resistance It is the resistance offered by Diode under reverse bias

Diode Current Equation I = Io (ev/η. vt -1) I = Diode Current V = External Voltage I 0 = reverse saturation current η = 1 for Ge, 2 for Si VT = k. T/q = T/11600; k=1. 38 x 10 -23 J/K , q=1. 6 x 10 -19 C T = Temperature of Diode (K) = (0 C + 2730)