ECE3040_Exam3_Solution

ECE3040_Exam3_Solution - ECE 3040 Microelectronic Circuits...

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Unformatted text preview: ECE 3040 Microelectronic Circuits Exam 3 April 23, 2010 Print your name clearly and largely: \S L) /1,( if] 0 [/1 Instructions: 1. Closed book, closed notes. You are allowed to use 1 sheet of notes (single side, letter size) as well as a calculator. 2. Show all work in order to receive full credit for your answers. Incorrect answers may be awarded partial credit when appr0priate. 3. CIRCLE YOUR FINAL ANSWER WITH THE PROPER UNITS INDICATED. Write legibly. If I cannot read it, it will be considered a wrong answer. 4. Do all work on the paper provided. Clearly indicate which problem you are solving on each page. Turn in all scratch paper, even if it did not lead to an answer. 5. There are 12 pages to this exam, including the cover sheet and 6 blank pages. There are 100 total points in this exam. Observe the point value of each problem and allocate your time accordingly. Good luck! Part l:( 40 points) Multiple Choice Select the best answer: 1.) (4-points) For a MOS capacitor with substrate contact grounded a.) accumulation occurs if the gate bias voltage is larger than 0 for p-type substrate. b.) threshold voltage is smaller than 0 for p-type substrate. 0.) depletion occurs when the gate bias voltage is larger than 0 for n-type substrate. @. .. inversion occurs when the gate bias voltage is less than the threshold voltage for n-type substrate. 2.) 4-points) An enhancement mode NMOS transistor has a ...p-type substrate b.) ...a channel under the gate when there is no applied gate voltage 0.) ...p-type channel when biased into cutoff (1.) None of the above 3.) (4-points each, 12-points total) For the three transistor cross-sections I, II and 111 shown below, answer each of the three questions a-c: I. II. III. a.) For VGS>VDS>0 which cross-sectional view (I, II or III) is correct. II. b.) For 0<VGS—Vt<VDs which cross-sectional view (I, II or III) is correct. I- c.) For VGS<0 and VDS>0 which cross—sectional view (I, II or III) is correct. . I II _ 4.) (4-points) For a current amplifier designed for maximum gain, a.) You should have a high input impedance and a high output impedance. b.) You should have a high input impedance and a low output impedance. l You should have a low input impedance and a high output impedance. '.) You should have a low input impedance and a low output impedance. 5.) (4-points) In the MOSFET amplifier to the right, WITHOUT doing any calculations, estimate the voltage gain. a-) ngL b.) R2/R1-l-R2 0'.) One . Can not be determined without VT 6.) (4-points) Circle ALL WCE transistors below... 1') D 1: FT G U j ()———I ~——O If 0—~ I I - 5 ill- g—-|I<—-—O I} I 8.) (4-points) Which of the following is true for feedback circuits. a.) Feedback in a voltage amplifier can decrease the input resistance. b ) Feedback in a voltage amplifier can increase the output resistance. 0.) Feedback in a voltage amplifier can increase the amplifier bandwidth if the open loop gain is larger than the closed loop gain. (1.) Feedback in a voltage amplifier can decrease the amplifier bandwidth if the open loop gain is larger than the closed loop gain. Part 2: (40 points) 0]) Amp Circuit Analysis 9.) (20 points) Assume that the 01) amps are ideal. 21.) (IO points) Derive ilic transfer function A\-(S)=Vm.1(S)/an(5). b.) (10 points) Determine the input and outpm impedance. 1-— f I L.“ F11 s—e—umgx‘ 1k i (:1 10H 32 100 Vail)- ‘v L i S ) .. I . 'ui ., , __ ix Hk air-L HE?”‘"".‘ E; "\ I i I 5 i ________ wig—ww- rJ-f "I - m :2 ‘* M f. ,,::::::jr"““‘“” 5L aim“ ._._ J\_[ F—‘i firm ______, ._L- r S I? L i‘ L I I .1 7 n.1,. r—"" .4 ‘1 [Ia fl i 1:1,; Hi}, _-’— {P “‘ , I X W S Extra work can be done here. but clearly indicale with problem you are soiving. . )5“! HWJS ” ~\ La 1: ~- "*7 ''''''''''''' -~~——*—R /v.) l‘klwtfs * "/Cfica(’ I’f‘iVlC’Fs—S ‘ "'“W -»- \ .. X A_- : ,4 T 5 L7 “ ...... #E'JMFM- -_ I f_ i 5 h: a U _ _WH_F____H___‘_ ‘_ I“? I-i' 1m \ (em 3 / 60 C _ \___J_H ._‘M” ,g- I 10.) (20—points) Determine the voltage gain ot‘the foliowing circuit. Assume the 0p amps are ideal. Ex.“ .—‘ _ W 7 ———~ * 35; i ’ - ‘\ Vout ” if i I ' 3,4, _.-__-—.r.7———-£3—-- - x l‘ r . 2/ /+._ , ./ \ g ‘3‘",- " '. l- 7 1/" | W M e} : H fl r“ EULK i 1304 5004 «,‘fu‘ + \Afifnw L—\N‘.Ig\, AVD‘A 3‘1? '5‘; .0 VCL l _._ __. K}? \/'L"\. " My *Lf K A :3 Vu'vx : W 4,33,. V K a}? .\ C > Kai {\- i; ,/. E ._.-._._ _:_ ./ V,“ ‘ .___ ,3 x, :x ix ,I We Km kt €0le >< Souk AV 1 V "" "’ : .____“ _____ New : . e m, : Part 3: (20 points) MOSFET Amplifier 1 1.) (20-points) Derive the voltage gain, input resistance (Rm) and output resistance (Rom) of the following amplifier. You may assume all capacitors have infinite capacitance. MOSFET transconductance is gm, and the output resistance 1'0 is infinite. Grading will be based as such: 5 points for converting the circuit into equivalent small signal circuit, 5 points for deriving the voltage gain, 5 points for deriving the input resistance and 5 points for deriving the output resistance. Extra work can be done here, but clearly indicate with problem you are solving. SWIM,” “Thad Cf|YCLLf|Pf Extra work can be done here, but clearly indicate with problem you are solving. @ Input—f Yen‘s-(qua Rim SMCQ AAOJFET flora CHM/@111 :0 ...
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