freq response

freq response - ECEN 326 Electronic Circuits Frequency...

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ECEN 326 Electronic Circuits Frequency Response Dr. Aydın ˙ Ilker Kar¸ sılayan Department of Electrical and Computer Engineering
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High-Frequency Model High-Frequency Model C in v 1 f C 1 g m v g mb v 2 E or S 2 r in r x B or G o C or D v r B General BJT MOS r x r b 0 r in r π C in C π C gs C f C μ C gd r o r o r o g m g m g m g mb 0 g mb ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 1
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Active BJT: C π = C b + C je = τ F g m + C je C μ = C μ o 1 - V ψ o n C π ± C μ MOS: C gs = 2 3 WLC ox C gd : Overlap capacitance C gs ± C gd ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 2
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Transition Frequency, f T Transition Frequency, f T o C f 1 g m in v 1 r v r x C r o i in i i i o i i i i i o i o i i (s) g m r in 1 + r in (C in + C f )s ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 3
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Transition Frequency, f T Transition Frequency, f T i o i i (j ω ) g m r in 1 + r in (C in + C f )j ω At high frequencies: i o i i (j ω ) g m (C in + C f )j ω ± ± ± ± ± ± ± ± i o i i (j ω ) ± ± ± ± ± ± ± ± ω = ω T = 1 g m (C in + C f ) ω T = 1 ω T = g m C in + C f , f T = ω T 2 π BJT: ω T = g m C π + C μ MOS: ω T = g m C gs + C gd ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 4
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Small-signal circuit C R S R L V i V o 1 R S R L V i V o g f C in v 1 r in L v o r v m R x o R v r i S ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 5
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Transfer function v o v i (s) = K 1 - s C f g m 1 + a 1 s + a 2 s 2 K = - g m R OL R R S + r x = - g m R OL r in R S + r x + r in a 1 = C f R OL + C f R + C in R + g m R OL RC f a 2 = R OL RC f C in R = (R S + r x ) k r in R OL = r o k R L ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 6
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D(s) = 1 + a 1 s + a 2 s 2 = 1 - s p 1 1 - s p 2 | p 2 | ± | p 1 | ⇒ p 1 ≈ - 1 a 1 , p 2 ≈ - a 1 a 2 p 1 = - 1 R C in + C f 1 + g m R OL + R OL R p 2 = - 1 R OL C f + 1 RC in + 1 R OL C in + g m C in N(s) = 1 - s z 1 z 1 = g m C f ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 7
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Miller Approximation Miller Approximation V Z x Z i V o i -A Z i = V i I i = V i V i - V o Z x = V i V i - ( - AV i ) Z x = Z x V i (A + 1)V i = Z x A + 1 Z x = 1 sC Z i = 1 s(A + 1)C = 1 sC 0 , C 0 = (A + 1)C ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Frequency Response 8
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Miller Capacitance Miller Capacitance C f in v 1 r in C v o v 1 g m R L r o i v x R S +r Miller Approximation C in v r in 1 o v v 1 g m
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freq response - ECEN 326 Electronic Circuits Frequency...

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