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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.) (4points) For a MOS capacitor with substrate contact grounded a.) accumulation occurs if the gate bias voltage is larger than 0 for ptype substrate.
b.) threshold voltage is smaller than 0 for ptype substrate.
0.) depletion occurs when the gate bias voltage is larger than 0 for ntype substrate.
@. .. inversion occurs when the gate bias voltage is less than the threshold voltage for ntype
substrate. 2.) 4points) An enhancement mode NMOS transistor has a ...ptype substrate
b.) ...a channel under the gate when there is no applied gate voltage
0.) ...ptype channel when biased into cutoff
(1.) None of the above 3.) (4points each, 12points total) For the three transistor crosssections I, II and 111 shown below,
answer each of the three questions ac: I. II. III. a.) For VGS>VDS>0 which crosssectional view (I, II or III) is correct. II.
b.) For 0<VGS—Vt<VDs which crosssectional 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.) (4points) 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.) (4points) In the MOSFET ampliﬁer to the right, WITHOUT doing any calculations, estimate the voltage
gain.
a) ngL
b.) R2/R1lR2 0'.) One
. Can not be determined without VT 6.) (4points) Circle ALL WCE transistors below... 1') D 1:
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I 8.) (4points) 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
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AV 1 V "" "’ : .____“ _____ New : . e m, : Part 3: (20 points) MOSFET Ampliﬁer 1 1.) (20points) 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 CfYCLLfPf 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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 Spring '07
 HAMBLEN
 Input impedance, Electrical parameters, Microelectronic Circuits, high input impedance, gate bias voltage

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