Exam (elaborations) TEST BANK FOR Electronic Devices and Circuit Theory 11th Edition By Robert L. Boylestad, Louis Nashelsky (Solution Manual)

Copper has 20 orbiting electrons with only one electron in the outermost shell. The fact that the outermost shell with its 29th electron is incomplete (subshell can contain 2 electrons) and distant from the nucleus reveals that this electron is loosely bound to its parent atom. The application of an external electric field of the correct polarity can easily draw this loosely bound electron from its atomic structure for conduction. Both intrinsic silicon and germanium have complete outer shells due to the sharing (covalent bonding) of electrons between atoms. Electrons that are part of a complete shell structure require increased levels of applied attractive forces to be removed from their parent atom. 2. Intrinsic material: an intrinsic semiconductor is one that has been refined to be as pure as physically possible. That is, one with the fewest possible number of impurities. Negative temperature coefficient: materials with negative temperature coefficients have decreasing resistance levels as the temperature increases. Covalent bonding: covalent bonding is the sharing of electrons between neighboring atoms to form complete outermost shells and a more stable lattice structure. 3.  4. a. W = QV = (12 μC)(6 V) = 72 μJ b. 72 × 106 J = 19 1 eV 1.6 10 J      = 2.625 × 1014 eV 5. 48 eV = 48(1.6  1019 J) = 76.8  1019 J Q = W V = 76.8 10 19 J 3.2 V   = 2.40  1018 C 6.4  1019 C is the charge associated with 4 electrons. 6. GaP Gallium Phosphide Eg = 2.24 eV ZnS Zinc Sulfide Eg = 3.67 eV 7. An n-type semiconductor material has an excess of electrons for conduction established by doping an intrinsic material with donor atoms having more valence electrons than needed to establish the covalent bonding. The majority carrier is the electron while the minority carrier is the hole. A p-type semiconductor material is formed by doping an intrinsic material with acceptor atoms having an insufficient number of electrons in the valence shell to complete the covalent bonding thereby creating a hole in the covalent structure. The majority carrier is the hole while the minority carrier is the electron. 8. A donor atom has five electrons in its outermost valence shell while an acceptor atom has only 3 electrons in the valence shell. 2 9. Majority carriers are those carriers of a material that far exceed the number of any other carriers in the material. Minority carriers are those carriers of a material that are less in number than any other carrier of the material. 10. Same basic appearance as Fig. 1.7 since arsenic also has 5 valence electrons (pentavalent). 11. Same basic appearance as Fig. 1.9 since boron also has 3 valence electrons (trivalent). 12.  13.  14. For forward bias, the positive potential is applied to the p-type material and the negative potential to the n-type material. 15. a. 23 19 (1.38 10 J/K)(20 C 273 C) 1.6 10 C K T kT V q           25.27 mV b. / (0.5 V) / (2)(25.27mV) 9.89 ( 1) 40 nA( 1) 40 nA( 1) VD nVT D s I I e e e        0.789 mA 16. a. 23 19 ( ) (1.38 10 J/K)(100 C 273 C) 1.6 10 K T k T V q           32.17 mV b. / (0.5 V) / (2)(32.17 mV) 7.77 ( 1) 40 nA( 1) 40 nA( 1) VD nVT D s I I e e e        11.84 mA 17. a. TK = 20 + 273 = 293 23 19 (1.38 10 J/K)(293 ) 1.6 10 C K T kT V q         25.27 mV b.   / 10/(2)(25.27 mV) 197.86 ( 1) 0.1 A 1 = 0.1 A( 1) VD nVT D s I I e e e           0.1  A 3 18. 23 19 (1.38 10 J/K)(25 C 273 C) 1.6 10 C =25.70 mV K T kT V q          ID = ( VD / nVT 1) s I e  8mA = ( (0.5V) / (1)(25.70 mV) 1) (28 108 ) s s I e   I  8 8 mA 2.8 10 s I   = 28.57 pA 19. ( VD / nVT 1) D s I  I e  6 mA 1 nA(eVD /(1)(26 mV) 1) 6 106  eVD / 26 mV 1 eVD/26 mV  6 106 1 6 106 /26mV 6 e e log eVD  log 6 10 26 mV D V = 15.61 VD = 15.61(26 mV)  0.41 V 20. (a) x y = ex 0 1 1 2.7182 2 7.389 3 20.086 4 54.6 5 148.4 (b) y = e0 = 1 (c) For x = 0, e0 = 1 and I = Is(1  1) = 0 mA 21. T = 20C: Is = 0.1 A T = 30C: Is = 2(0.1 A) = 0.2 A (Doubles every 10C rise in temperature) T = 40C: Is = 2(0.2 A) = 0.4 A T = 50C: Is = 2(0.4 A) = 0.8 A T = 60C: Is = 2(0.8 A) = 1.6 A 1.6 A: 0.1 A  16:1 increase due to rise in temperature of 40C. 22. For most applications the silicon diode is the device of choice due to its higher temperature capability. Ge typically has a working limit of about 85 degrees centigrade while Si can be used at temperatures approaching 200 degrees centigrade. Silicon diodes also have a higher current handling capability. Germanium diodes are the better device for some RF small signal applications, where the smaller threshold voltage may prove advantageous.