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Unformatted text preview: ECE 100 Second Midterm Examination Fall 2009 This examination is closed book, you may not use any reference materials or any calculator.
Be sure to show your work carefully. No credit will be given for unsupported answers. 1. Consider the circuit sketched to the right. The opamp has '~ —
“ideal” input and output resistance, but its gain is A(s) = (3/5 W L! '1 mH
where G = 107 rfs. __ _ __ ; ["
(a) Find the feedback transfer function B(s) = V_._ New. FLyIN ,l __ (b) Plot the magnitude and phase of the loop gain T((o) on a {1%.} ril'aaMF' Bode Plot. “"' " your
(c) Find the phase margin and Sh0w it on the Bode plot. i D r.
(d) Show exactly how to add 45” to the phase margin. " 2. Consider the circuit sketched to the right. The opamp . _—— — L
has “ideal” input and output resistance, but its gain is W I '
A(s). The circuit has two output terminals labeled A and _ ,2 __i ___l' 555f"""3“""ip ("X7} Z —
Find Vac, 150201” and draw 3 Norton equivalent circuit i for the “black box” with output terminals A and B. m '
3. Consider the voltage follower circuit sketched to the right. The opamp has “ideal” input and output resistance, €53,151 I but its gain is A(s) = Gr’s where G = 107 rfs. The feedback g OHM? transfer function is a delay of 100ns due to a transmission “tr” v ElamMT
line. The Laplace transform of a delay 1: is exp(sr). —_ _. (a) Find the loop gain T(s). Va M (b) Plot the magnitude and phase of the loop gain T(to) on iE '. a Bode Plot.   j " (c) Find the phase margin and Show it on the Bode plot. IECEIOO MONTE/<1)? 3L sow _F7HL?£Cﬂ g—f‘W—a
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 Spring '09
 Phase margin, loop gain, output resistance

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