Download Current Source - Introduction to Microelectronic Circuits - Exam and more Exams Microelectronic Circuits in PDF only on Docsity! 1 EE 40: Introduction to Microelectronic Circuits Spring 2008: Midterm 2 Venkat Anantharam 03/19/08 Total Time Allotted : 50 min Total Points: 50 1. This is a closed book exam. However, you are allowed to bring two pages (8.5 x 11) notes, with writing on both sides. 2. No electronic devices, i.e. calculators, cell phones, computers, etc. 3. Show the steps used to arrive at your answer, where necessary. Partial credit will be given if you have the proper steps but an incorrect answer. A correct answer for a problem involving multiple steps where it is not clear how you arrived at the answer may not be given full credit. 4. Write your final answers into the boxes. 5. Remember to put down units. Last (Family) Name: First Name: Student ID: Lab Section: Signature: Max Score 1 (a-g) 10 1 (h-k) 10 2 6 3 (a) 4 3 (b) 4 4 10 5 6 Total 50 1. (20 pts total) − − 2 In the circuit shown above the current source is a DC source. The switch is open prior to time 0, and the current has reached steady state prior to time 0. At time 0 the switch closes. The reference configuration to use for each circuit element in solving the problem is shown in the figure. Please provide all answers in terms of Is , R, L, and C . (a) What is iL (0− )? (2 pts) (b) What is vC (0− )? (2 pts) iL(0 ) = (because cap is open circuit in DC steady state) vC (0 ) = (because inductor is short circuit in DC steady state) (c) What is iL (0+ )? (1 pt) (d) What is vC (0+ )? (1 pt) iL(0+) = iL(0−) = Is vC (0+) = vC (0−) = 0 (j) Write down a differential equation that vC (t) must satisfy for t ≥ 0. (4 pts) (k) For what combination of parameter values is the circuit critically damped for t ≥ 0+ ? (Note: if your answer depends on Is , you have done something wrong). (2 pts) 2. (6 pts) In the circuit above the two sources are at different frequencies ω1 = 200rad/sec and ω2 = 100rad/sec respectively. Use superposition and phasor analysis to determine iC (t). arctan 2 = 63.435◦ arctan 4 = 75.96◦ 3. (8 pts total) Consider the circuit above operating in AC steady state at frequency ω = 1000rads/sec. (a) What is the average power dissipated in the resistance? (4 pts) There are several ways to do this. The easiest is to work directly with the resistor. Using voltage divider, Pavg =
