Assignment Physics Semiconductor Electronics Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 Ph 011 47623456 Assignment Physics Chapter Semiconductor Electronics 1 Which of the following is a correct statement with regards to semiconductor devices 1 Doping a semiconductor decreases its carrier concentration 2 Doping with pentavalent atoms makes the semiconductor negatively charged 3 A n type semicoductor will have more conductivity compared to p type for same extent of doping 4 nenn in is true only for intrinsic semiconductor 2 2 Which of the following is true with regards to Zener diode 1 It can act as a voltage regulator 2 Breakdown in it takes place due to collision of the energetic free electron with the bonded pair of electrons within the depletion region 3 A Zener diode can never be forward biased 4 All of these 3 Find the current flowing through R1 in the circuit below assuming the diodes to be ideal R3 V 10V s R2 R1 1 R 10K R 5K R 5K 2 3 1 Zero 2 0 5mA 4 3 1mA A pure semi conductor has equal electron and hole concentration of ne nh 1016m 3 Doping by indium increases nh to 4 5 1022 m 3 What is ne in the doped semi conductor 1 106m 3 2 1022m 3 4 2mA 3 2 2 109 m 3 4 4 5 109 m 3 5 When N type semiconductor is heated 1 Number of electrons increases while that of holes decreases 2 Number of holes increases while that of electrons decreases 3 Number of electron and holes remains same 4 Number of electrons and holes increases equally 1 6 In the given circuit the current through the resistor 2 k is Vz 12 Volts Assignment Physics Semiconductor Electronics 1 k 20 V 2k 1 2 mA 2 4 mA 3 6 mA In a half wave rectified sinusoidal output the peak value of voltage is V0 The rms value of the output is 4 1 mA 7 0V 2 0V 2 02V 1 2 3 0V 4 8 Two identical p n junction diodes are connected in series with a battery in 3 ways as shown np n p np np i ii n p n p The potential difference across the two p n junctions are equal in 1 i and ii 3 iii and i 9 During a zener breakdown in a p n junction diode iii 2 ii and iii 4 i only 1 Minority carriers acquire sufficient kinetic energy from the electric field and collide with a valence electron the bond will be broken and the valence electron will be taken to the conduction band 2 Once a zener breakdown occurs the potential difference across the diode increases significantly with the increase in the applied battery potential 3 Zener breakdown occurs in the forward bias mode 4 Breakdown is produced by direct breaking of covalent bonds due to the high electric field 10 In a light emitting diode LED 1 Light is emitted when the diode is reverse biased 2 The p n junction is lightly doped 3 Has an advantage of the emitted light being nearly monochromatic 4 Has a long warm up time 2 Assignment Physics Semiconductor Electronics 11 In the diagram the input is across the terminal A and C and the output is across B and D Then the output is B C A D 1 Zero 3 Full wave rectified 2 Same as the input 4 Half wave rectified 12 The intrinsic concentration of electrons and holes are 2 1013 cm 3 at 300 K in germanium If the germanium is doped with phosphorus atoms with dopant concentration of 1016 cm 3 find the hole concentration in the doped semiconductor 1 4 1010 cm 3 2 2 1010 cm 3 3 5 109 cm 3 4 5 1011 cm 3 E E 1 3 CB VB CB VB 13 The following four options have side by side comparison of energy levels in intrinsic semiconductor and n type semiconductor Where is the depiction correct E CB VB donor level E CB VB Acceptor level E E 2 4 CB VB CB VB E CB VB donor level E CB VB Acceptor level 14 A Zener diode has a breakdown potential of 15 V and is a part of a circuit shown in figure below Find the current through the 3 K resistor 1 5 mA 3 6 33 mA 3k 25V 2k 2 3 33 mA 4 3 67 mA 3 15 A silicon specimen is made a p type semi conductor by doping which is on an average one indium atom per 5 107 silicon atoms If the number density of atoms in the silicon specimen is 5 1028 atoms m3 then the number of acceptor atoms in silicon per cm3 will be Assignment Physics Semiconductor Electronics 1 2 5 1030 3 1 0 1015 2 1 0 1013 4 2 5 1036 16 In semiconductor at a room temperature 1 The valence bond is partially empty and the conduction bond is partially filled 2 The valence bond is completely filled and the conduction bond is partially filled 3 Valence bond is completely filled 4 The valence bond is completely empty 17 If the voltage between the terminals A and B is 17V and Zener breakdown voltage is 9V then the potential voltage across R is A B R 3k R 5k L 2 8V 4 17V 1 6V 3 9V 18 When p n junction diode is forward biased then 1 The depletion region is reduced and barrier height is increased 2 The depletion region is widened and barrier height is reduced 3 Both the depletion region and barrier height are reduced 4 Both the depletion region and barrier height are increased 19 A pure semiconductor is known to have an electron concentration of 7 07 1015 m 3 Doping by indium increases the concentration of holes to 5 1022 m 3 Find the concentration of conduction electrons in the doped semiconductor 1 7 1015 m 3 3 5 1022 m 3 2 1 109 m 3 4 12 1015 m 3 20 In a zener regulated power supply a zener diode having a zener breakdown voltage equal to V is used as shown in the figure If the current through the diode is 5 mA then the breakdown voltage of diode is 250 1000 20V 5mA 2 15 V 4 0 1 10 V 3 5 V 21 With an AC input from 50Hz power line the ripple frequency is 1 50 Hz in the D C output of half wave as well as full wave rectifier 2 100 Hz in the D C out put of half wave as well as full wave rectifier 3 50 Hz in the D C output of half wave and 100 Hz in D C output of full wave rectifier 4 100 Hz in the D C output of half wave and 50 Hz in the D C output of full wave rectifier 4 Assignment Physics Semiconductor Electronics 22 The current through an ideal p n junction shown in the circuit diagram will …