Table of contents  
Diode  
Applications of Diodes  
Junction Transistor  
Current Relationship in BJT 
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➤ Semiconductor Diode:
➤ Biasing of a Diode:
There are three different techniques that are used to analyse circuits that contain diodes:
If Bipolar transistor is treated as single node, they by Kirchhoff's current law
I_{E} = I_{C} + I_{B}
This relation is applicable in all three configurations of BJT.
➤ Relation between current gain
For dc mode, common emitter current gain
β = I_{C}/I_{B}
And common base current gain
α = I_{C}/I_{E}
Applying these expressions in above equation,
➤ Relation between leakage current
For common emitter configuration,
I_{C} = α(I_{C}+I_{B}) + I_{CBO}
⇒ I_{C} = α(I_{C} + I_{B}) + I_{CBO} (I_{E} = I_{C} = I_{B})
⇒ (1  α)I_{C} = αI_{B} + I_{CBO}
⇒
Since the current equation for the common base configuration is as
I_{C} = βI_{B} + I_{CEO}
Comparing above both equations,
I_{CEO} = I_{CBO}/1α
or I_{CEO} = (1 + β)I_{CBO}
Example: A transistor has I_{B} = 25 μA, β = 100, I_{CBO} = 100 nA. Calculate a, I_{C}, I_{E} and I_{CEO}.
Solution: β = 100
α = β/(1+β) = 100/101 = 0.99
I_{C} = βI_{B} + (1+β)I_{CO}
= 100 x 25 x 10^{6} + 101 x 10^{9} = 2.51 mA
I_{E} = (I_{B} + I_{C})
I_{E} = (0.025 + 2.51) = 2.535 mA
I_{CEO} = I_{CBO} + (1+β) = 101 x 100 x 10^{9} = 10.1μA
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1 videos33 docs64 tests
