Layout - Introduction to Microelectronic Circuits - Exam, Exams of Microelectronic Circuits

Download Layout - Introduction to Microelectronic Circuits - Exam and more Exams Microelectronic Circuits in PDF only on Docsity! EECS40, FALL/2001 MIDTERM #2 Professor Oldham • 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 recieve full or partial credit. • This exam contains 6 problems and corresponding worksheets plus the cover page. • Do not ask questions during the exam. If you believe there is an error, please point it out. If you believe there is an ambiguity, explain your interpretation in your answer. NMOS Equations: if VDS>VDSSAT ID = IDS (1 + lambda VDS) ID = kVS W/L (VGS-VT) Problem #1 Shown below is the layout of a CMOS circuit. The mask boundaries are indicated in a few places. The connection to ground (VSS),(VDD), the output F, and the two inputs A and B are identified on the layout. A cross section through X-X is also shown below, and the materials are identified. (a)Draw the circuit diagram and rearrange it to be a reasonably neat drawing. Obviously, the drawing should contain only NMOS and PMOS transistors and wires. You must, of course, label the inputs, outputs, and power supply connections. (b)Write the truth table for the logic circuit. (Voltage of VDD means logical 1.) USE THIS AREA FOR ROUGH LAYOUT, BUT PUT ANSWER IN LAYOUT BOX BELOW J PRACTICE AREA PMOS transistor layout | 0.25um = LL (b) NOTE: The metal drawn is just the start. It should be extended to the contact areas. TO SOURCE Active Area (thin oxide) N-Well ome TO —————= GATE Polysilicon 1 7 y! ; ><] Contact ~ PMOS transistor layout ANSWER AREA TO DRAIN 0.25um ole  Problem #3 (a)Find the thevenin equivalent of the circuit in the box. you must draw it in the answer box provided on the page opposite side. (b)Find the norton equivalent of the circuit in the box. you must draw it in the answer box provided on the page opposite side. (c)Through a series of tests you find that the circuit in the box Q has thevenin equivalent shown, but you really do not know what is in the box. You now consider power flow under two conditions: 1) The box is short circuited (wire connected across C-D) 2) The box is loaded by connecting a 10k resistor ("load") across terminals C-D. Which of the answers on page 6 correctly describe the power dissipation in the box and in the load? Problem 3 Work and Answer sheet (a) (b) (c)Which answers below (if any) correctly describe the power dissipated within the box and the power dissipated in the load (short or 10k resistor)? Any number from zero to all 6 may be correct. Circle correct statements. 1) when shorted the power dissipation in the box is a minimum. 2) when shorted the power dissipation in the box is a maximum. 3) when shorted the power delivered by the box is zero. 4) when loaded (10k) the box delivers 10mW to the load. 5) when loaded (10k) the box delivers 2.5mW to the load. 6) when loaded (10k) the dissipation within the box is 2.5mW. t (msec) 10 20 Vour 7 (msec) Problem #5 Consider the NMOS transistor whose I versus V characteristics are shown in the figure below. This is a device with W=2um, L=0.2um. Note that the straight line portion of the I-V curve, when extrapolated to the voltage axis, intersects at -25V. Note also the we determine the threshold voltage to be approximately 0.5V from these characteristics. (a) Based on these I-V characteristcs, determine IDS, kVS and Lambda for this transistor biased at VGS=2.5V. Put the answers in the answer boxes on page 10. (Note that the NMOS I-V equations in saturation are given on the coversheet of the exam.) (b) If VDS=2.5V, what values of VGS would be required to achieve a drain current of exactly 1mA? (c) We note that for drain voltages exceeding 1V, the device behaves much like a current source (actually, a "sink" since the current is going into the drain). So suppose we model it as an ideal current source in parallel with a resistor, as shown below. What are the numerical values of IDD and RDD for VGS=1.5V? Problem 5 Answer sheet (a) IDS = ----------------- units? kVS = ----------------- units? Lambda = ----------------- units? (b) VGS = ----------------- units? (c) IDD = ----------------- units? RDD = ----------------- units?