Semiconducting Devices Question 120
Question: In the study of transistor as an amplifier, if $ \alpha =I _{c}/I _{e} $ and $ \beta =I _{c}/I _{b}, $ where $ I _{c},I _{b} $ and Ie are the collector, base and emitter currents, then
[CBSE PMT 2000; KCET 2000; Orissa JEE 2005]
Options:
A) $ \beta =\frac{1-\alpha }{\alpha } $
B) $ \beta =\frac{\alpha }{1-\alpha } $
C) $ \beta =\frac{\alpha }{1+\alpha } $
D) $ \beta =\frac{1+\alpha }{\alpha } $
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Answer:
Correct Answer: B
Solution:
As we know $ i _{E}=i _{C}+i _{B} $
$ \Rightarrow \frac{i _{e}}{i _{c}}=1+\frac{i _{b}}{i _{c}} $
$ \Rightarrow \frac{1}{\alpha }=1+\frac{1}{\beta } $
$ \Rightarrow \beta =\frac{\alpha }{1-\alpha } $ .
