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Electrical Engineering 40 - Fall 1999 - Oldham - Midterm 2

Electrical Engineering 40 - Fall 1999 - Oldham - Midterm 2...

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Unformatted text preview: UNIVERSITY OF CALIFORNIA College of Engineering Depmment of Electrical Fxlgimering and Computer Sciences Professor Oldham Fall 1999 EECS 40 —— MIDTERM #2 10 November 1999 Name: ' Student ID: Last. First TA: Cl Kusuma CI Chang Guidelines: 1. Closed book and notes except 1 page of formulas. You may use a calculator. Do not unstaple the exam. Show all your work and reasoning on the exam in order to receive full or partial credit. 9'95“!" This exam contains 12 pages plus the cover page and 2 sheets of scratch paper included at the end of the exam. You can remove these from the rest of the exam if you wish. Points Your Problem Possible Score --- -—- 5 What is the value of the unknown node voltage in each of the following circuits? Assume diodes are perfect rec— tifiers " , (a) sv 10V _ ‘T'lv VAB — Lil-:VCD= 77y (f) A cross-section for a CMOS chip is shoWn on the facing page. Some node voltages are indicated. Please tell us what the values are for the node voltages at nodes U, W, R S. {6.133 UR.“ 5walUu~5V “OT TOM lpf'svw: Qv ' 10110 Prob l Worksheet 20f10 W Shown on the opposite page is the layout and two cross—sections through a CMOS inverter. A list of components follows. You are to indicate, by labelling, the location of that feature on the figure. The first question is used as an example. 2.1mm W (1) A contact to polysilicon [EXAMPLE] (a) well region [(2) gate of NMOS transistor (b) field oxide (3) the W dimension of the PMOS transistor (c) NMOS gate oxide (4) contact to p-type substrate ‘ (d) metal contact to PMOS source or drain (5) metal contact to PMOS gate (e) poly on field oxide (6) spacing from n+ source gain areas to well mask (0 metal over field oxfle » (7) input electrode ' v (g) contact to NMOS source or drain (8) output electrode . (h) oxide over polysilicon gate 2.1mm A possible list of masks for this process follows. You are to order the masks by simply filling in the mask num— ber. It 15 possible that one or more masks 18 missing. If so, you must fill out anew mask row for each missing mask MASK# FUNCTION 4 (GI-“— a. (:33 _ ' ® “a- n_ Define areas for gate oxide Ital-— _ --— ‘ Fill in mask # here M! For this layout what do we expect for the relationship between gate delay for output rising (5110. and output falling (tpHL)? Answer by putting in the correct symbol 1n the box (= > or <) Putsymbol here _ . ‘PLH ‘PHL Why? MOS l? ‘> :5 LoMee 3of10 CMOS INVERTER Redrawn Layout from SIMPLer O xide Mask CF=Clear Field, DF = Dark Field 1 _ NOTEhn ‘6 answerng this question, put numbers ONLY on layout, and only letters on cross-sections ‘3 ':':';':-:-:-:-:-:-:-:~. :-:-:-: u'u'u'n'r-‘u'u'u'u'u'h'h'mgn'r-a W You are trying to construct a dc switch with an MOS transistor, as shown below. The idea: When input is low, output high. But when input is high, output is hopefully low. V DD Note: For this transistor = IOfF/In'n2 = lttF/cm2 m2 for electrons V sec 11:1000c LOAD = 10pf (a) If VIN = 5V , what is the channel electron charge (coulombfcmzxfor small values of VOUT only)? _ Q 7-1 Cori (Vs-s“ VT) formula—4c” (W’s- UT T T It value 4'5- X '0‘; w“ s (b) If V1N = 5 V , what is the sheet resistance of the channel? (Again for the case in which VDUT is very small.) R n 1". '1'- formula ‘Z 2 a A; Q\ value Z2 Z JLZE] MEMO loco (c) What is the value of VIN needed to produce an output of 0.1 V? 5" Mu. =>LK5=J $X=JK .lv— ——? X' 434* VIN: 9.5V KER-n 7“;er- '-*>RD=5'BUJ1/fl * W =7>Vos" ‘11-": 3" (d) If the input suddenly switches ogw. and the load' 18 10 pF as shown, sketch the output voltage versus time (accurately) and estimate the time At for the output to go from 0.1 V to 2. 45V (halfway to 5 V). “ALF-Duh? a) At=.6‘( RC At: 33,8 nsec 50t10 (d) time 60110 A CMOS inverter drives an off-chip capacitance load, as shown below. All you know about the MOS transistors is shown in the graphs. (DO NOT ASK-{Or more information!) , . y’Ime‘A) "V35? .- t / i 'Vosp — 3V ’VCSp .. 2v 'VGSp _ 1v ‘VDSp was .. 3v —VGS = 2V —vGS = 1V VDSn (a) Draw the circuit model (in the box provided on opposite page) for the circuit (replacing transistors with appropriate simpler elements, such as voltage sources, current sources, resistors, capacitors, inductors) when VlN = 3V . .No numerical values are required in part (a). _(b) Suppose V1N suddenly switches to 0V at t = 0" . Draw the new circuit model in the box provided (again with simpler elements). Show both the general form an_=d the numerical values for all parameters. (c) Sketch the form of VOUT versus time for t = 0+ to t 4-) no on the axes provided. (No numbers needed.) ((1) What is the time delay for VOUT to go to VDD/Z (in n sec)? '1 = Ry x CQAD’ 0.68 I , 2-. 5‘3 A: ll (e) At what time does VOUT equal 1 V (in n sec)? Vowt-Ct) 2 ‘3 , 3 e—wt 1:" == ‘3 6363*" V LOH x‘C. _ 70f10 (a) (b) (c) PUT CIRCUIT HERE --—-> for VIN = 3V PUT CIRCUIT for VIN = 0 (RP $7917.. '_ VW': 3VW 12m “37’5le 80f10 W (a) You open Up your Robot Kit and find the following circuit. You suspect it is a linear voltage amplifier. You know the differential amplifier has very high internal gain. (3.1) Is it a linear amplifier? ‘ Vo (a. 2) If so, what 15 the voltage gain -- °? [If not, ignore (a. 2). ] (8.3) If not, why not? Linear amplifier? ‘ or No) V. V ' 0 signal 333KB + - ail; +5.2v_, . , Av 5 "\7'. = Z O o to +250 mV -Rail = 0v ‘ _ A“ v L-fl-qo ‘+ “1"0- 20 If not, why not? to (b) You also find the following circuit. Again you suspect a linear amplifier. You know the differential ampli- fier has very high internal gain ”’ (b. 1)Is it a linear amplifier? (b. 2) If so what 15 the voltage gain? [If not, ignore (b. 2). ] (b. 3) If not, why not? '500K_ V. O to 3:51.21ng Linear amplifier? Yes or V. V ‘L—@’— V AV 5 —9 - ‘ +Rail = +5.2V Vi M 03" 9 - 411mg ov _ I If not, why not? f‘ F EEC} B ‘C k (Arr a. M 1. s) (c) Carefully sketch the curve of V001" versus VIN for circuit (a) on the graph axes provided for , osviszsomv. (d) Carefully sketch the curve of VOUT versus VIN '- for circuit (b) on the graph axes provided for o sv‘i s 250mV. 90f10 (e) (d) . , -_—.-,— ..4... . ,DK 500K 9%.”; W W Vx: Swim P‘l" OFg 1V w‘fi: H vi- '= {104 v ' mono ...
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