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Question
Output characteristics of an n-p-n transistor in CE configuration is shown in the figure.
Determine:
(i) dynamic output resistance
(ii) dc current gain and
(iii) ac current gain at an operating point VCE = 10 V, when IB = 30 μA.
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Solution
(1) Dynamic output resistance is given as:
`R_0 = ((ΔV_(CE))/(ΔI_C))_(I_b constant) = 12 - 8/(3.6 - 3.4 xx 10 ^-3) = 4/(0.2 xx 10 ^-3)=20 kΩ`
(2) d.c current gain .`β _(d.c) I_c/I_B = (3.5mA)/(30μA) = (3.5 xx 10^-3) /(30 xx 10^-6) = 350/3 = 116.67 `
(3) a.c current gain, `β _(a.c) = (ΔI_c)/(ΔI_B) =((4.7-3.5)mA)/((40-30)μA) = (1.2 xx 10^-3)/(10 xx 10^-6) = 120`
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