Differential Amplifier - Microelectronic Devices and Circuits - Exam, Exams of Microeconomics

Download Differential Amplifier - Microelectronic Devices and Circuits - Exam and more Exams Microeconomics in PDF only on Docsity! University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Sciences R. T. Howe (Spring 1993) EECS 105 Final Examination: May 17, 1993 Ground Rules: Closed book; three 8&#189 " x 11" crib sheets (both sides)• Do all work on exam pages• Answers within &#177 10% of the correct answer will recieve full credit.• Default bipolar transistor parameters:• Default MOS transistor parameters:• Page 1 1. Two-Stage BiCMOS Differential Amplifier [20 points] (a) [2 points] Draw the differential half circuit for Stage 1. EECS 105 Final (Spring 1993) 1 (b) [4 points] Draw the differential two-port small-signal model for Stage 1 and find the numerical values of its parameters. Page 2 (c) [4 points] Draw the differential two-port small-signal model for Stage 2 and find the numerical values of its parameters. (d) [4 points] Find the numberical value of the small-signal gain vo/s. Page 3 (e) [2 points] What is the maximum DC common-mode input voltage, VCM,max, for which all devices are forward active (BJT) or saturated (MOS)? (f) [2 points] What is the minimum DC common-mode input voltage, VCM,min, for wich all devvices are forward active (BJT) or saturated (MOS)? (g) [2 points] What is the DC power dissipation for this amplifier? Page 4 2. Pictorial MOS Electrostatics [20 points] EECS 105 Final (Spring 1993) 2 (a) [4 points] Find the DC voltages at the drain of M2 and at the source of M 2. (b) [4 points] Find the small-signal voltage gain avo=vo/vs at low frequencies (consider Cc open). Page 7 (c) [4 points] Given that the magnitude (in dB) plot for the voltage gain has a pole at 2kHz (see plot), find the numerical value of Cc. You may assume that any Miller capacitor dominates all other device capacitors (e.g., Cgs). (d) [4 points] Find the frequency for which the magnitude of the small-signal voltage gain |av|dB=0dB. If you couldn't solve part (b), assume that avo=14,000. EECS 105 Final (Spring 1993) 5 (e) [4 points] Given that the channel length of all MOSFETSs is L=3 &#181 m and that the oxide capacitance per unit area is Cvo=14,000. (d) [4 points] Given that the channel length of all MOSFETs is L=3 &#181 m and that the oxide capacitance per unit area is Cox=0.5 fF/&#181 m&#178 (1 fF=1E-15 F), find the differential imput capacitance of this op amp. Page 8 4. Dynamic MOS Logic [20 points] (a) [4 points] What logic function is implemented by this dynamic logic gate? Use the + sign for "OR", a dot for "AND", and an oversocre for "NOT". There is no need to simplify the expression. Hint: transistor M1 fuctions to "pre-ground" the load capacitance CL, using clock waveform (t). (b) [4 points] How short a 5-V clock pulse (length T ) can be used to pre-gound the load capacitance, assuming that the minimum T is 5 times the propagation delay found in discharaging CL from 5 V ot 0 V? Hint: consider the appropriate transistor to be saturated in finding the propagation delay. Page 9 (c) [4 points] Sketch vE(t) on the graph below, for the case where A, B, C, and D are 0 V when t=T . You are given that vE(0&#175 )=5 V just before the clock transitions to 5 V at t=0. (d) [4 points] What is the propagation delay for the situation in part (c) (all inputs low when the clock goes low)? You can consider that M2 is so wide that it fuctions as a short-circuit when it's "on". (e) [4 points] What is the propagation delay when A, B, D = 0 and C = 1 (5 V) when the clock (t) goes low? If you couldn't solve part (c), assume that its answer was tp=1 ns. Page 10 5. Small-signal CMOS current amplifier [20 points] EECS 105 Final (Spring 1993) 6 (a) [4 points] Redraw the schematic, replacing all transistor current sources by the current-source symbol (with the numerical value indicated) and all transistor voltage sources by batteries (with the numberical value indicated). (b) [4 points] What is the numerical value of the input resistance Ri of this current amp? . Page 11 (c) [4 points] What is the numerical value of the output resistance (don't include the load resistor, of course!) for this current amp? (d) [4 points] What is the short-circuit current gain Ai (vo a small-signal short to ground) for this current amplifier? Draw the two-port model for the amp. (e) [4 points] What is the overall current gain io/iin with the 100 k load resistor connected to the amplifier? Page 12 &#169 1994 by R. T. Howe translated to HTML by Walter Hsiao Eta Kappa Nu (November 1995) EECS 105 Final (Spring 1993) 7