exam_pastd

# exam_pastd - (270(34 1(a Show that the resistivity of...

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(270) (34) 1 3 21 19 10 5 026 0 048 0 10 6 1 1 026 0 1 026 0 1 026 0 1 m / atoms Indium x . ) . ( x . ) . ( e p . ) p ( e ) p n ( e m . P P P P P P P N P P P = µ = = µ µ + µ = σ = σ = ρ (a) Show that the resistivity of intrinsic (pure) silicon (Si) is 2278 - m. (b) A silicon is doped with Indium (group 3) atoms to 0.026 -m, find the type of silicon (n-type Si or n-type Si). Find also the indium atoms concentrations required. Hence find the electron concentrations in the silicon. (c) If the silicon is doped with 10 20 /m3 arsenic atoms (group 5). Find the electron concentrations in the silicon. Given that σ = e(n µ n +p µ p ) , np = n i 2 , n i = 1.5 x 10 16 /m 3 , µ p = 0.048 m²/Vs, µ n = 0.135 m²/Vs , e = 1.6 x 10 -19 C. (34) (12) Hence dope Si with 5x10 21 Indium/m 3 . (a) The resistivity of intrinsic Si Density of electrons is given by (8) m m / x . ) . . ( x x . x x . ) ( en ) n n ( e i i N P i i P i N i σ = ρ = + = µ + µ = µ + µ = σ 2277 1 10 39 4 135 0 048 0 10 5 1 10 6 1 3 16 19 3 2 16 2 / 10 5 . 4 10 5 ) 10 5 . 1 ( 10 21 m electrons x x x p n n P i P = = = (6) (c) (5) (b) 3 20 / 10 m electrons (3) p-type Si

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(16) Find V O / V S in terms of R, C and jw. If C = 1 µ F , R 1 = 1k , R 2 = 10k , find the complex transfer function G (= V O / V S ). Is the op amp circuit a low pass filter? Assume the op amp is ideal. (16) 2 (12) ω + = µ ω + = ω + + = ω + + = = k j k * * j R R CR j R R C j R R V V G S O 1 1 10 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 1 2 S V R 2 V O R 1 C R 1 (4) Circuit is a high pass filter
(21) 3 In an op amp filter circuit, the complex transfer function G (= V O / V S ) is given as. (a) Find ω O and plot the magnitude of G ( | G | ) versus the angular frequency ω . Show clearly the value of | G | when ω = and ω = ω O in your plot.

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exam_pastd - (270(34 1(a Show that the resistivity of...

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