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Unformatted text preview: 487 CHAPTER 13 Exercises E13.1 The emitter current is given by the Shockley equation: − = 1 exp T BE ES E V v I i For operation with 1 exp have we , >> >> T BE ES E V v I i , and we can write ≅ T BE ES E V v I i exp Solving for BE v , we have mV 4 . 718 10 10 ln 26 ln 14 2 = = ≅ − − ES E T BE I i V v V 2816 . 4 5 7184 . − = − = − = CE BE BC v v v 9804 . 51 50 1 = = + = β β α mA 804 . 9 = = E C i i α A 1 . 196 μ β = = C B i i E13.2 α α β − = 1 α β 0.9 9 0.99 99 0.999 999 E13.3 mA 5 . = − = C E B i i i 95 . / = = E C i i α 19 / = = B C i i β E13.4 The base current is given by Equation 13.8: − × = − − = − 1 026 . exp 10 961 . 1 1 exp ) 1 ( 16 BE T BE ES B v V v I i α which can be plotted to obtain the input characteristic shown in Figure 13.6a. For the output characteristic, we have B C i i β = provided that 488 V. 0.2 ely approximat ≥ CE v For V, 0.2 C CE i v ≤ falls rapidly to zero at . = CE v The output characteristics are shown in Figure 13.6b. E13.5 The load lines for V 0.8 and V 8 . in = v are shown: As shown on the output load line, we find V. . 1 and V, 5 V, 9 min max ≅ ≅ ≅ CE CEQ CE V V V 489 E13.6 The load lines for the new values are shown: As shown on the output load line, we have V. . 3 and V, 7 V, 8 . 9 min max ≅ ≅ ≅ CE CEQ CE V V V 490 E13.7 Refer to the characteristics shown in Figure 13.7 in the book. Select a point in the active region of the output characteristics. For example, we could choose the point defined by mA 5 . 2 and V 6 = − = C CE i v at which we find A. 50 μ = B i Then we have . 50 / = = B C i i β (For many transistors the value found for β depends slightly on the point selected.) E13.8 (a) Writing a KVL equation around the input loop we have the equation for the input load lines: 8000 ) ( 8 . in = + − − BE B v i t v The load lines are shown: Then we write a KCL equation for the output circuit: CE C v i = + 3000 9 The resulting load line is: From these load lines we find 491 , A 5 A, 24 A, 48 min max μ μ μ ≅ ≅ ≅ B BQ B I I I V 3 . 8 , V 3 . 5 V, 8 . 1 min max − ≅ − ≅ − ≅ CE CEQ CE V V V (b) Inspecting the load lines, we see that the maximum of v in corresponds to I B min which in turn corresponds to V CE min . Because the maximum of v in corresponds to minimum V CE , the amplifier is inverting. This may be a little confusing because V CE takes on negative values, so the minimum value has the largest magnitude....
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This note was uploaded on 11/20/2011 for the course ELE 220 taught by Professor Anas during the Spring '11 term at American Dubai.
 Spring '11
 Anas

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