Exam_3_Soln

Exam_3_Soln - Last Name: First: 1 Section: Ozturk001/...

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Last Name: First: 1 Section: Ozturk 001 / Escuti 002 (Circle one) ECE 200 - Fall2007 - Exam 3 Instructors; M.J. Escuti & N.A" Masrrari Instrucfions: 1) Closed book / ClosedNotes. 2) No scrap paper. 3) Calculators are NOT allowed. 4) Show your work step by step so we can give partial credit when possible. 5) Be neat - we should be able to read/follow what you wrote. Problem I (10 pts) Consider a25W audio amplifier designed to drive a 4C) speaker. The system is designed for an input signal with a maximum RMS value of 10mV (for example from an iPod). (a) [7 pts] What voltage gain must the amplifier have? (evaluate answer fully for full credit) / -V^, -Y*-^, -Vo^Pl-^t d..=-=- ' v,n v*_n vo_pt_n p . -v;* =25w where R = 4Cl. Thus v*-*,= Ji6o =lIv . 'ut- R n,= ,*=*=tooo (b) t3 ptsl If a dual power supply confrguration is used, what are the smallest power supply voltages that will avoid clipping the maximum input signal? The arrplitude of a signal corresponding to an RMS value of 10 V is V-_^, =Vo,,o X42 =l4.l4V q4tP. #l #2 #3 #4 #5 #6 #7 #8 Extra Survey Total 10 15 l0 l5 t5 5 4 100 Thus minimum power supply voltage that can be used to avoid chpping ;s E-f A f + V,
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Last Name: measured. (a) t3 ptsl Determine the equation for vi"(t) ThePeriod of the inPut signal is T =Ims * f =l =IOOO Hz T v,,Q) = Q50 ml) cos (?nl 000t (b) t3 pts] Determine the equation for v.ot(/) Since the output has the same frequency and phase as the inPut, then First: 2 Section: Oaurk 001 / Escuti 002 (Circle one) vin(t) (in mv) -250 vout(D (in v) l0 (c) ptsl Determine the voltage gain of the anplifier' vo*(r) {inv) tr -Vorr= 5 =Zo "v v,, 0.25 (d) t6 ptsl Sketch the transfer characteristic for this amplifier in the plot provided below' 14 12 10 8 o -400 -300 -200 100 200 300 4oo v,n(/) (inmV) 1.0 1.5 r (in ms) -100-2 4
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Last Name: First 3 Section: Ozturk 001 / Escuti 002 (Circle one) Problem 3 (10 Pts total' 2 each) An amplitude-modulated signal can be written as v^-(t)* Fv.Q)vr(r) where v"(t) is the carrier sinusoidal signal, urii) contains both the modulating signal v^(t) and a DC offset voltage, and /: Volts-l is only for correct unit conversion' Consider the following AM signal in the time domain, where it is known that the amplitude of the carrier sinusoidal is 10V: v".(t) = (20V)cos(2a50,000t) + (6Y)cos(2r 55,000f) + (62)cos(2r 45,000t) modulated is v,-(t) =v.(t)LY* +v^(t) and for the situation indicated above, it is clear that not only is the carrier a sinusoidal signal, v.(t)= A"cos(Zrf"f),butthemodulatingsignalis
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This note was uploaded on 03/20/2008 for the course ECE 200 taught by Professor Escuti during the Fall '07 term at N.C. State.

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Exam_3_Soln - Last Name: First: 1 Section: Ozturk001/...

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