ECE 3040 Microelectronic Circuits

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1 ECE 3040 Microelectronic Circuits Exam 3 April 18, 2014 Dr. W. Alan Doolittle Print your name clearly and largely: Instructions: DO NOT TAKE APARTANYPAGES OF THIS EXAMAND SHOWALL WORK ON THE PROVIDED PAGES. Read all the problems carefully and thoroughly before you begin working. You are allowed to use 1 new sheet ofnotes (1 page front and back), your two note sheets from the previous exams as well as a calculator. There are 100 total points in this exam. Observe the point value ofeach problem and allocate your time accordingly. SHOW ALL WORK AND CIRCLE YOUR FINAL ANSWER WITH THE PROPER UNITS INDICATED. Write legibly. IfI cannot read it, it will be considered a wrong answer. Do all work on the paper provided. Turn in all scratch paper, even ifit did not lead to an answer. Report any and all ethics violations to the instructor. Good luck! Sign your name on ONE ofthe two following cases: I bid NOT observe any ethical violations during this exam: I observed an ethical violation dunng this exam:

2 Fint 20% Multiple Choice and TrueIFalse (Select the most correct answer) 1.) (~-poin~s~~als~: The voltage at the end ofthe pinched off channel ofa MOSFET biased m~tlon IS always V D-SAT = VGS-VT. 2.) (2-pointa:alse: The effective mobility is lower than the bulk mobility because the gate's el. leld forces carriers to interact with the defective SiOiSi interface. 3.) (2-points) True~e MOSFET's transconductance,~, is determined by the slope of the Ios-Vos curve ana only is non-zero if A, the channel length modulation parameter, is nonzero. :::: V~~ t<'-o 4.) (2-point~ False: For a PMOSFET a negative gate voltag~ i~e~eded to drive the mos capacitor"imoinversion. e... ~ 5.) (2-poineFalse: A current amplifier should ideally have zero input impedance. 6.) (2-points) Tru~ For a MOSFET l}mplifier, clipping occurs when the output is large enough to driv~sistor into sa~ion and cutoff. p"ear 7.) (2-points) Tr ~ alse: With every new generation that shrinks proportionally in size, Intel must redesign e old circuit to account for different los values. ~ca II\~ 8.) (2-points) Tru~ Common s~e amplifiers have a gain of -1, a very high input impedance and~tput impedance. C. 0 9.) (2-pointselse: Ifamplirying a voltage from a signal with a very high source impedance' a ph meter, the voltage amplifier should also have a very high input impedance, possibly even amplified by using feedback. 1O.)(2-points) True! : (In honor ofapril 15 th that just passed ) Currently in America, the lower 50%. come earners in America pay Jess than 3% of Federal Income tax while the top 5% of income earners pay -57% ofall taxes. In other words, -112 of Americans can vote higher taxes on others but do not pay any federal taxes themselves astounding! Reference

3 A tub ~-? dlela /, ~ 11.) (lo-points) An amplifier has an open loop gain of200 VN. a open loop bandwidth of 100 Hz, and an input impedance of look ohms and an Output impedance of 100 ohms. Show work: t R;", 1" Rf)v1-+ a) Determine a percentage ofthe output voltage that can be fed back to the negative terminal to result in a closed loop bandwidth 00 KHz. J J V' I. G A 7}(/'en '::: ;-..00 IV %'::: U- &'a;l-\ 64ntf,'w":df-h frcj)l<.c'f-"~ C()h$'/qh1: ~ ;; (:00 "Iv)(iOO H,) ==(flc}"f'j )(~OOO) ="? Mff'J= {, 67'v~ G,66 -= A-(!)pe~... ).()O _ (,66 t (3 "J.(X}(t.16)-:: ;).(}O ; I..,.. P A,.. - I l' tl;).()o.-.:7 ~ -=,!!O - C.l6 :::) ~ r, ~~~~ b) For your answer in part a). what is the new closed loop gain? Ae--{P7eJ =- - e. b, 6'6 VIv c) For your answer in part a), what is the new input impedance (at DC i.e. do not worry about the frequency response)? {}, (I a A ) R! (/(,\... I + IT ff"d'ea 'Y\."Ai2 1"'\ ~ltxetf fi " D -t 0,/4-,(.;100II to<7tr f!5:~) 3 f>~ Jl 7 d) For your answer in part a), what is the new output impedance (at DC - i.e. do not worry about the freq uency response)? I!., u. 'I flppn I t I AtJle" 100

4 11.)(20-points) Because your professor is so nice, the opamps used in the circuit below can be considered ideal. There are two outputs Voutl and Vout2 and one input VinAC. Determine the closed loop gains VoutlNinAC and Vout2NinAC and plot both gains on a Bode plot. ",-&;J / - -,: v V1nAC ~------I+ U '..... Vant('mna rv I OPAMP, OPAMP R5 99k R3 v R4 19k C if 837p 1k r Vout2 R6, o i ~ 111" - _.--'---~ - V/v I t\f:.1'ifr 100

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6 Pulling all the concepts together for a useful purpose: 10) (50-points) Given the following amplifier circuit, (a) Identify the configuration of the stage (common~. (b) What is the AC voltage gain, VouJVin? You may assume all capacitors have infinite capacitance and all inductors have infinite inductance. Additionally consider the circuit to be operated at low frequencies where you can neglect all small signal capacitances. Grading will be based as such: part a=5 points, part b=18 points for DC solution (gate, source and drain voltages along with drain currents), 12 points for the conversion to the small signal model and 15 points for small signal analysis. SHOWALL WORK TO GET CREDIT!!!!! C S c..o ~~ Idc1 75e-6 9V Vin Rsource ~ + rv 1Meg M2 R4--1 > BOK 12V ----~.--' Use the following parameters (note that K, V T and Avary with transistor type): For PMOS Depletion Transistors: K p '=40 uan 2 V T = +3.0V A=O.O V-l Length (L)=10 urn Width (W)=10 urn rll '. For PMOS Enhancement Transistors: K p '=30 uajv 2 V~ -1.75V A=O.l V-I For NMOS Depletion Transistors: K n '=l ua/v2 V~ -1.0V A=O.l V-I Length (L)=10 urn Width (W)=10 urn Length (L)=0.18 urn Width (W)=18 urn M ") \ For NMOS Enhancement Transistors: rl rj. \ K n '=50 ualv 2 V T = +1.0V A=O.O VI Length (L)=1.8 urn Width (W)=18 urn

7 (J.t'1 v- l Extra work can be done here, but clearly indicate with problem you are solving. l ~C I /t~5«-- >.-q."r-vl-iq" :l - MI : VGS I ~ 0 l'"s" 75'~ /! ::; ~Qe-b~~0 -ti)) (r-/oj ~ t G,e-6) I'fI -::: \~+e(, (+0. 1 v P5 ).,,,~ )Ve- Vos / V6'S' -.-vr 1- l' l' () -IV "V V~= ~ V VOl -=" V(t;'). -::! V'S +- 1O~ 1R3- )).. V ~ 5' + Q~)l.A) 1()~ - }). V

8 -,,, V6/ ;... II VGS;t - 5',5" - V6,~ ;... /I ::: 0 ~ -,,' VCS." -j.. 10 V 6S a.. 1-5'.,,, 0 [y. ::: ~ G ~ ;:::'" rl) ': ~ 5'0~., (.l.~6-i);). _1~..,).. U ".!'ps '"?,'t'" ()f"" (, hec: lr',. - () I If't V 5;> C-U.1df'r - I~ +1;,$ ;l RG+ VO~.. I05 4 R~ -if ~ 0 V05 ': ~l - Jq(/1A(1I(~"2f'\+ 111:k) VOS-: G,7l( V V0 7? \4-s -VT ~ I VOSJ f ~ I05f -.L~5;; (::Z)J

9 Extra work can be done here, but clearly indicate with problem you are solving. \ Ptes~). AL " (\) tvjs' :: 1l1;~ r< I ~,+R$~rc.e

ECE 3040 Microelectronic Circuits

ECE 3040 Microelectronic Circuits Exam2 N"v, SqJt,e,n:j,e, 9, 2015 Dr. W. Alan Doolittle Print your name clearly and largely: nstructions: Read all the problems carefully and thoroughly before you begin