This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: UNIVERSITY OF UTAH ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT EE/CS 5720/6720 Analog Integrated Circuit Design Midterm March 20, 2002 \
NAME: E { EEICS 5720 EHCS 6720
circle one (Please print) 0 Do not open the exam until instructed.
a Draw a circle or box around your ﬁnal answers. . All answers shOuld include units (e.g., V, mA, m) where appwpn‘ate. For
frequencies, use Hz (or kHz, or MHz), not radiansfsecond. o If you want partial credit on incorrect answers, show your work on the pages you
turn in! If you choose to turn in any sheets of scratch paper, write your name on
those sheets! 0 Don‘t spend all of your time on one difficult problem. Don’t be afraid to skip
ahead if you get stuck. You don’t have to work the problems in order. a Good luck! l. (15 points) Consider the opamp shown below. You may assume that all the
transistors are operating in active mode. Q10 Isms VDD=V53= 3 V Isms: SOﬂA
spec; = 40 pm? pﬂco, = 120 pm!
V", = le = 0.8 V VA = 40 V (for all devices)
(W/Lh = (W/L); = (W/L); = (W/Lk = (W/L)m = 100
(W/L); = (W/Lh = 50 (W/L)g= (W/L); = 200 (Wag/no
Cc = 5 pF 031
(a) What is the gain ofthis ampliﬁer, in dB? \\ S X"
x. l ' _ .2 47 J."
3%, _ a", (6.4%), ID. — 2.4%N1.f00. 29—“ ’2 f’q/V 0‘01 61;)“ Kg“
3m?” 2/016»: (EJ715157 ‘W .: /o?5;wq/V ’A‘Dc'vtﬂiw )3
VT! 3 .: VA 9 ‘0
” WW 5917, .— /.(M.(Z Av : Afﬁrﬁs N5 is U‘
rat" : (Tl/c E all} r: 5,00 kg : 3m, (fdsziit‘djq‘) 9m7(rdr(”ralg:h  1
(b) What is the'dtihminam pole frequency, in Hz? : 3 ”7‘ 5’35"! = ”‘6’, 309 l
“ (Hull"c1393 Cccmm W 54?, :S‘mml/x «ﬁller : “Jo _ __. 
(“ed 74" 27, h 901 (ll/‘1'! (c) What is the slew rate, in Wps? \ Allfmxit “(mi“m I'  t 9‘93 _ @1‘
“‘1‘ CW we“  —
/ c 4"
/
.   fame ﬂﬂMr.
am
*7 jun {’03 3 9"" “BWFnJae‘} 2. (20 points) Twostage opamps are commonly used because single—stage ampliﬁers
typically yield insufﬁcient gain. However, a highgain singlestage ampliﬁer can be built
if cascode transistors are added to boost the drain resistance of other transistors.
Consider the singlestage ampliﬁer shown below. VDD Qw Isms Q3 Ignore the body effect in all calculations. (a) Write an approximate expression for the gain As of this ampliﬁer. You answer should
contain only gm’s and r435 of particular transistors. A“ 5 3%" (”53 3"6’m’f // ”’7 7'»; K357) \\ / (“4““le (’{FQC‘I Oﬁ Ctrdirt 06410“; (EffrJMQ Valgzd'rdsq (b) Assume all transistors have the same widthtolength ratio WIL. Derive an expression
for the source voltage of Q] if the input commonmode voltage is zero. Assume V» > 0
and Vs; < 0, and all devices are in active mode. Your answer should contain some (but not necessarily all) of the following terms: 13;”, W11, MC“, V“, “DC“, Vrp. F ”f? fox W _. 2. (continued) (c) Derive an expression for the maximum allowable value of chp that keeps all
transistors in active mode, assuming the input commonmode voltage is zero. Your
answer should contain some (but not necessarily all) of the following terms: 13m. WIL, .“rICox; Vm, Macon Vrp (d) Derive an expression for the minimum allowable value of chy that keeps all
transistors in active mode, assuming the input commonmode voltage is zero. Your
answer should contain some (but not necessarily all) of the following terms: Isms, WIL, MC“, Van lupcan Vip \/ .
(ArcN V5: ‘l' Vﬁgq L V657 3. (10 points) Circuit design often involves tradeoffs between smallsignal ac
performance (e.g., gain), and largesignal dc performance (e.g., voltage swing
limitations). Consider the following commonsource ampliﬁer: The transistor has an Early voltage VA. Let Vourmn be the minimum output voltage that
keeps the transistor in active (saturation) region. Express the gain of this circuit (A) in
terms of VA and VOUTmin only. To Evade Q)“ in Sak'i'kr‘a'i‘mij V0r1> Vc‘mj‘l I 10;
_ 21 , 21“
ya) ‘ V_.._2—~ 2 PH
QQI udThrn 4. (20 points) We are testing a nMOS transistor fabricated in a new CMOS process. The device has a width of 211m and a length of 2pm. We set the substrate and source voltage
to zero volts. We make the drain voltage equal 5V. With the gate voltage at 1.0V, we measure 8.0uA of drain current. With the gate voltage at 2.0V, we measure 98.0uA of
drain current. (a) What is the nMOS threshold voltage of this process? (You may neglect channel
length modulation effects.) Circle your answer! *0 “1 £7..an '2! [Val—£49): 9,141 = siwsczxﬂVgﬁ } ?
73M 3 ELL/u .(Lx {ZFHQL (b) Given that the gate oxide' 15 made of SiO; and has a thickness of 150 A (15 nm), What
is the electron mobility in this process? Express your answer in units of cm [(Vs).
Circle your answer! /”‘u (a: :_./UO/Mﬂ/ﬁ/1 {la/9"? qﬁw’f) l4”? 0.€V fan ‘“ ”(OO/V/q/VZ 12
(ex _ Zox  6a _ 3.7 e 3.3579“? F" : 2,3010% 7F/ch  NM 1’ {4350: J
/?E aﬂoat/6'71”“ Suppose we now test a pMOS transistor in this process. The device has a width of 2pm
and a length of 2pm. We set the well and source voltage to 5.0V. We make the drain
voltage equal zero volts. With the gate voltage at 3.5V, we measure 9.8% of drain
current. With the gate voltage at 2.5V, we measure 57.811A of drain current. (0) What is the pMOS threshold voltage of this process? (You may neglect channel—
length modulation effects.) Circle your answer! ((1) Given that the gate oxide is made of SK): and has a thickness of 150 A (15 nm), What
is the hole mobility in this process? Express your answer in units of cmle' 5). Circle
your answer! 5. (20 points) Consider the commonsource ampliﬁer shown below. Assume the current source is ideal (i.e., it has an inﬁnite output impedance). Assume that Early voltage is
preportional to transistor length. (a) If we decrease the transistor length L by a factor of two, what happens to the gain and
bandwidth of this simple ampliﬁer? The gain increases; a factor of M 2*
circle a : The bandwiﬁf: lincreases )decreases) by a factor of 2'
‘ ' 019 one (b) If we decrease the bias current I by a factor of two, what happens to the gain and
bandwidth of this simple ampliﬁer? The gai ‘ decreases by a factor of ‘l a ‘ e one The bandwidth a factor of 2
circle a  6. (15 points) Consider the ampliﬁer shown below. Ignore the body effect in all calculations. (a) Derive an approximate expression for the gain Av of this ampliﬁer. You answer
should contain only gm’s and rds’s of particular transistors. Hint: You may ﬁnd it useful
to draw a smallsignal model, substituting the T model for Q; and Q;. You may neglect
r035 and r431. A” / __ ..— fwd: fa( //% 7M ‘1
M34 3:: Jrgﬁf gw + 4”? “i 1&0“ 7a,» A __ (Ar? ﬂﬁ’ﬁ; (I * ?M%m7)]
f
V 6;: * ”M“ 5w * 77M (b) If all transistors in this ampliﬁer have the same widthtolength ratio WIL, derive an
expression for the minimum allowable commonmode input voltage to keep all
transistors in active mode. Your answer should contain some (but not necessarily all) of the following terms: 13m. WKL, AC“, Vm, “9C“, KP. V‘“Cmm:n: V3“; 4' V65; +. 5x! ZIBJAI + Z IE
IA
We: Cox“ .. [4"4 6 :1 ...
View
Full Document
 Fall '10
 M.Ismail

Click to edit the document details