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

(a) Dynamic output resistance

(b) DC current gain and

(c) AC current gain at an operating point V_CE=10V, when I_B=30 A.        

Dynamic output resistance is given by,

For I_B = 30 A,  = (12-8) = 4V and  = (3.6-3.4) = 0.2 mA

Therefore, output resistance,  

 ii) dc current gain is given by, 

At  = 10 V and I_b = 30 A

I_c = 3.5 mA

=  = 117

iii) AC current gain is given by,  

 At V_CE = 10 V, = (3.5 -2.5) mA = 1 mA and 

 = (30 -20) A = 10 A