ECSE_330_december2004

ECSE_330_december2004 - McGill University Faculty of...

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Unformatted text preview: McGill University Faculty of Engineering Department of Electrical and Computer Engineering ECSE—330A — Introduction to Electronics H“ ;// llll v“ I n.- Examiner: Dr. David V. Plant; \ _ . ' " / _ ,x/ f .. Associate Examiner: Dr. Ramem'hari (signature on file) flan-1&3? ' "L'L't' 35’" "fit-"ew- - r. ’ Date: Tuesday, December 21, 2004 Time: 2:00 — 5:00 Calculator: Faculty Standard Pertinent Information: 1) This is a closed-book examination, no notes permitted. There are 3 pages of equations provided at the back of the examination. 2) The examination consists of 6 problems; you must answer all 6 problems. 3) The examination is worth T0 total points 4) The examination consists of 10 pages, including this page and the equations pages; please ensure you have a COMPLETE examination paper. 5) Only the Faculty Standard Calculator is permitted. 6) Questions may be completed in any order, however ensure that you clearly identify which part of which question you are attempting. Do NOT turn in this exam with your exam booklet Question #1 (9 pts.): A transresistance amplifier with input resistance 1000, output resistance 1509, and open-circuit transresistance 400WA is rectified by adding a feedback diode as shown below. A current source with a source resistance 1.21;!) is applied at the input. You may assume the 0.7V-drop model for the diode. (part e) I I I I : |L Vout : l I : RL I I | I Rout For parts a), b), c) and (1) there is no load attached (Vout is an open-circuit). a) [2 pts._| Redraw the circuit and replace the amplifier with its equivalent circuit. (Note: Leave the diode as it is, do not replace it with its small signal model). b) [2 pts.] Give the voltage gain VouttVin when the setup is in the linear region of operation (i.e. before clipping occurs at Vout). c) [2 pts.] At what value of IS does clipping occur at Vout‘? d) [1 pt] Determine the output resistance, Rout, during linear operation. (Note: you may assume Is is open-circuited from the input to find Rout). For part (e), the diode has been disconnected. e) [2 pts.] A load, RL = 509 has been added at the output as shown in the diagram. Determine the current gain, Al, of the setup. (Hint: Ai=lljls). Question #2 (13 pts): In the following circuit, all diodes are identical. Use the constant voltage drop model. +3V +3V A A +lV A 5000 1m g “W. __ 03 3;}? 06 :2 z \ D1 5 D4 RP = “VA r‘-\ 2 m 50;] C1 IICICJ —i/‘|— x 02 / _n-.f-._;‘\,_._ - |_. __ a ------- ——— l—f—“VO | VA 2‘ VB - , Ve I _' ' Wily \02 fl“: D5 ”i‘\. (3 \‘/’ ‘JJ 2’ 1kg ‘ " |2=10rnA ‘3 ‘1V _3V _3V — a) [2 pts.] Assume V3 is a DC source and sketch the voltage transfer curve of VA vs. V3 for VS values from ~3V DC to +3V DC. Mark all relevant points on the plot clearly. For parts 1)). c) and d), assume Vs = v” a small—signal voltage source with UV DC. Use 1; = 0.68mA and Hp = 100.9. h) [4 pts.] Find the DC current passing through each diode in the circuit, (19; through I95) and also the DC voltage of V3 and V3. Clearly specifv your assumntions and justify them. c) [2 pts.] Draw the small-signal equivalent circuit. Do NOT calculate the diode small-signal resistances; d) [2 pts.] Derive the expression of “PO/vs. Do NOT attempt to simplify. For part e), assume Rp = 0. e) [3 pts.j For what range of values of I; are both D4 and D5 OFF? DJ Question #3 (13 pts) In this circuit, all transistors are active and have the same B value. You must decide where to include or neglect the Early Effect in your analysis. You may refer to indicated resistances as parts of your answer (for example, you may refer to Ring in your expression for Rims) R-inA Vac VCC Vcc ‘ E T /\ A. E i I Rczm’ Va: I _ l ' (3‘ A | b I f') “j “E R Rm ' !—' "i '4: a, B1 K]: "I . t i REG _ 4: no . {Res J __8 c m E LT r \ 0 U1 8 'l ...... .. Rin a) [5 pts.] Draw a small-signal model for this circuit. b) [4 pts.] Find expressions for Rm, RM, RM and Ram in terms of the resistances and sm all-signal parameters of the transistors. c) [4 pts.] Find expressions for the voltage gains art/vs, v__./vx, VIN}. and vuulfvZ in terms of the resistances and small-signal parameters of the transistors. Question #4 (10 pts) Consider the circuit below. For all parts of this question, you must decide when to include CLM and the Body Effect for these PETS. A Von A /---\ | : | | 9 R \__1/ 1 2 * (‘2- Dz —o— —Al_j M2 00 r The following is known: - a=0.02v" and |th| = 1v 0 y = OJSV'E and (p = 1.2V . VG] =3V,V32= 1V 0 The power supply VDD = 5V and total current from this supply is 11H; 1' 4mA. o The PETS have the same kn’Wr’ 1.; value. a) [1 pt] What is the threshold voltage Vt for each FET‘? h) [2 pts] Assuming M2 is in saturation mode, calculate the value of kn’WfL for these FETS. c) [2 pts] Find the value ofng and a condition on Rm that places M2 in saturation mode. d) [2 pts] Draw the small-signal model for this circuit (do not evaluate small-signal parameters). 0) [2 pts] Find an expression for the gain vofvs (do not calculate). f) [1 pt] Find an expression for the input resistance, Rm. Question #5 (13 pts) Consider the multistage BiCMOS circuit shown here. For this circuit, you must decide whether or not to include (where appropriate) the Early Effect and CLM. You must include the Body Effect. T +1ov A x a 200k so : A+5V co ' \Ii' —3—l 61 Vs't'\l‘j' N“ "“ i m i 1m ~- ” _ T (A +5V IYIGE 200k “12.. ” no 4." I t fl 10.7k W 1:; RDz VSZffiI‘jzl : I (kl T ‘ l i [ Rm _ ! a) [2 pts] Assuming the BJT’s have [5:99, angl = 0.7V and I = 2mA, determine Vx, the DC voltage at node X. For the remainder of the question, you may assume that the FETs have equal gm and grub values (gli = gm)” = gmM and gmle = gmbh-‘IZ : gum“)- b) [3 pts] Draw the small-signal model for this circuit (do NOT calculate small- signal parameters) c) [3 pts] Assmning V52 = 0V, find an expression for vvasl and Rim. (1) [3 pts] Assuming m = 0V, find an expression for Vx/ng and Ring. c) [2 ptsl Find an expression for Win. Question #6 (12 pts) A PET differential-pair and two common-drain amplifiers are biased using current- mirrors as shown below. The diff-pair output, V01 = Vm-Vm, is amplified by the common-drain amplifier stage to produce a final diffErentiai output, V02 = Vgl-ng. All FETs in the diff-pair and common-drain stages are identical, but the ones in the current mirrors have different widths W1 and W2 as shown. Differential Pair Von VDD Common-Drain Amplifier Stage Roi i . Ema Current Mirror Array Neglect the Body effect. You must include CLM output resistances for the current mirror but neglect CLM elsewhere. Assume VDD=1.8V and Rm = Rm. a) [3 pts.] Analysis of the current mirrors reveals Vim=l.2V, Rim=12kQ, Wl =1 .2urn, and W2=3um. 1:0.02V'l and L is identical for all devices. Estimate the output currents, 10., and output resistances, Rm, at the outputs of the current mirror stages. (Note: all 3 stages have the same lui and R0,). b) [1 pt] What is the differential small-signal input resistance, Rin, of the PET diff- pair? Note: For the remaining parts, you may use given circuit parameters (i.e. Rm) and FET small-signal parameters. DO NOT use any numeric values. c) [4 pts.] Find expressions for the differential output resistances, Rm,” and Ema. (l lint: You may assume the V01 terminals are grounded for Roma). (1) [4 pts.] Give expressions for the differential gains, Vole = (Vm-mev... and VtiszuI = (VSPVSZquI- FORMULA SHEETS Diodes: 1': IS exp(v/HVT —1) BJTSI ic: :1 eXpQBE/ iEZOB‘i'DiB gig FEZQE g V} E 1c VE=E=£ {FE 13 gm [C FKIWHM 13,3: 05:1 [3+1 PETS: NMOS: . t ff: CU 0 VGS < VI In 3 0 Triodc: V05. > VI ID = k; %[(VGS — mm — ‘TV; ] V03 < V05 _ V: V > V Saturation: OS I 10 : é—k; g—(VGS w 1VI )2 (1 + ELI/m. ) Body effect: V! Z V”) + y( 2¢f + VSB _ {2gb}. ) PMOS: Cutoff: I. 7— 0 V05 > V: D _ J, 3 TrlOdei V05 < V! In : kp I ”“ V: )Vm _ 2 V05] V05 > V03 _ V: 17.. . < V 9 saturation: GS I In : fl}; _ V: )i (1 + 2LVHS) V05 < V03 _ V; Body effect: “4‘ = ‘Vm‘flt 32¢}. fiVw SMALL SIGNAL _ 2'51“ gm _ V03 _ If; gm 2 k1,: — + a“ . V05) W gm :m EVI'FJVVstx/Tn 10 ...
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ECSE_330_december2004 - McGill University Faculty of...

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