ECSE 334 Winter 2009 Midterm

The total capacitance associated with node x is then

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Unformatted text preview: C IN is: R IN = R S The open-circuit time constant associated with C IN is: τ IN = R IN C IN The pole associated with node IN is: ω IN = 1 ⁄ τ IN Node X: Using Miller theorem, Cgd1 is replaced by C gd 1 ( 1 + 1 ⁄ A M 1 ) between node X and GND. The total capacitance associated with node X is then: C X = C gd 1 ( 1 + 1 ⁄ A M 1 ) + C db 1 + C L 1 + C gs 2 The total resistance associated with C X is: R X = r o 1 || R L 1 || R 1 The open-circuit time constant associated with C X is: τ X = R X C X The pole associated with node X is: ω X = 1 ⁄ τ X Node OUT: The total capacitance associated with node X is then: C OUT = C gd 2 + C db 2 + C L 2 The total resistance associated with C OUT is: R OUT = R L 2 || R 2 The open-circuit time constant associated with C OUT is: τ OUT = R OUT C OUT The pole associated with node OUT is: ω OUT = 1 ⁄ τ OUT ECSE334 - Prof. Anas Hamoui Midterm - SOLUTION page 6 of 7 ECSE334 Introduction to Microelectronics Winter 2009 e) Assuming a dominant pole exists, estimate: i) the 3-dB frequency, based on the open-circuit time-constant approximation ω 3 dB ≅ 1 ⁄ ( τ IN + τ X + τ OUT ) ii) the unity-gain frequency Note: For simplicity, write your expressions using the previously-derived variables. ω t ≅ A M ω 3 dB f) Current sources IBIAS1 and IBIAS2 in Fig. 3 can be realized using, respectively, current sources Q3-Q4 and Q5-Q6, as shown in Fig. 4. Assume that the signal voltage at the gate of Q3 and Q5 in Fig. 4 is zero. For the expressions found in parts (b)-(d) for the circuit in Fig. 3, which variables must be replaced and by which variables in Fig. 4 must they be replaced, in order to obtain the corresponding expressions for the circuit in Fig. 4 ? Q3 Q4 Cdb3 Cgd3 vS RS Q1 Vbias Q2 vo Cgd5 Q6 Q5 Cdb5 Fig. 4 Exchange: • RL1 with ro3 (to account for the output resistance of current source IBIAS1) • RL2 with ro5 (to account for the output resistance of current source IBIAS2) • CL1 with Cgd3 + Cdb3 (to account for the effect of the internal capacitance of Q3 on the total capacitance at node X). • CL2 with Cgd5 + Cdb5 (to account for the effect of the internal capacitance of Q5 on the total capacitance at node OUT). ECSE334 - Prof. Anas Hamoui Midterm - SOLUTION page 7 of 7...
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This note was uploaded on 02/08/2012 for the course ECSE 334 taught by Professor Anashamoui during the Spring '10 term at McGill.

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