An npn BJT has gm = 38 mA/v, Cµ = 10-14 F, Cπ = 4 × 10-13 F and DC current gain β0 = 90. For this transistor fT & fβ are
A. fT = 1.64 x 108 Hz & fβ = 1.47 x 1010 Hz
B. fT = 1.47 x 1010 Hz & fβ = 1.64 x 108 Hz
C. fT = 1.33 x 1012 Hz & fβ = 1.47 x 1010 Hz
D. fT = 1.47 x 1010 Hz & fβ = 1.33 x 1012 Hz
Answer: Option B

fT = gm / 2π(Cπ +Cπ)
fβ = fT / β0
Given values:
gm = 38 mA/V
Cµ = 10^(-14) F
Cπ = 4 × 10^(-13) F
β0 = 90
Calculating fT:
fT = (38 mA/V) / 2π(10^(-14) + 4 × 10^(-13) F)
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