α- cut off frequency of a bipolar junction transistor:

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α- cut off frequency of a bipolar junction transistor:

1. increases with increase the base width.
2. increases with increase in the collector width.
3. increases with increase in the temperature.
4. increases with decrease in the base width

Correct Option: D

f_β =	gm
	2π(C_π + C_µ)

and f_β = f_α (1 – α)
If α is fixed for a transistor f_β ∝ f_α
For f_β to increase C_µ + C_π should decrease, and for capacitance to decrease width must increase,

C ∝	1
	d

i.e. emitter base width and collector base must increase which means base width must decrease.