Output characteristics of an n-p-n transistor in CE configuration is shown in the Fig. Determine

(i) dynamic output resistance (ii) dc current gain and (iii) ac current gain at an opererating point `V_(CE)=10V`, when `I_(B)=30muA`.

Explanation

(i) Dynamic output resistance is given as :
`R_(0)=((DeltaV_(CE))/(DeltaI_(c)))_(I_(b) "constant")`
`=(12-8)/((3.6-3.4)xx10^(-3))=(4)/(0.2xx10^(-3))=20k Omega.`
(ii) d.c current gain,
`beta_(d.c)=(I_(C))/(I_(B))=(3.5 mA)/(30 mu A)=(3.5 xx 10^(-3))/(30xx10^(-6))=(350)/(3)=116.67.`
(iii) a.c. current gain,
`beta_(a.c)=(Delta I_(c))/(Delta I_(B))=((4.7-3.5 )mA)/((40-30 )mu A)=(1.2 xx 10^(-3))/(10xx10^(-6))=120.`