EECE 310 Homework 2 with Solution, Fall 2007

American University of Beirut DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING EECE 310 – Electronics Fall 2007 – 2008 Due Tuesday October 16, 2007 Homework 2 1. A junction diode operating at a temperature of 33 degrees C has IS = 10-15 A and n = 1.05. (a) What is the diode voltage if the diode current is 0.1 mA? (b) What will be the diode voltage if the current increases by a factor of 50? 2. Find the operating point (ID, VD) for the diodes in the circuits shown below. Assume that all the diodes are ideal. 3. a. Assume that the diode in the circuit below is ideal. Find the operating point (iD, vD) of the diode. Hint: Use the Thévenin equivalent circuit. b. Repeat part (a) for a real diode at a temperature of 27 degrees C with n = 1 and IS = 10-16 A, using: i. Iterations with an initial guess for iD equal to the value found in part (a) ii. The graphical load line method. American University of Beirut DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING EECE 310 – Electronics Fall 2007 – 2008 Due Tuesday October 16, 2007 CAD Assignment 1 Use PSpice to analyze the circuit of Problem 3 in Homework 2. (Note: The PSpice tutorial from EECE 200 is available on Moodle.) Start by placing 4 resistors with the values shown, and a 13.8V DC voltage source. Make sure that your ground node(s) are named 0. The diode part to use is Dbreak from the BREAKOUT library. After placing the diode, right-click on its symbol, then click on Edit Pspice Model. Replace the .model line in the Model Editor with the following line: .model D_ideal D Is=1e-16 n=1e-6 The unusually small value of n (10-6) in this model makes the diode behave like an ideal one. Create a new simulation profile, (under the PSpice menu), and call it DC Analysis. What we are interested in for this circuit is an Analysis Type of “Bias Point”. Simulate your circuit, and observe the node voltages and branch currents, by clicking on the “V” and “I” buttons on the Capture toolbar. V1 13.8Vdc D_real D2 V1 R2 15k R1 18k V1 R3 10k R4 22k To simulate the circuit now with a real diode, right-click on the diode symbol, then click on Edit Pspice Model. Replace the .model line in the Model Editor with the following line: .model D_real D Is=1e-16 n=1 This value of n = 1 makes the diode behave like a real one, with a value of IS = 10-16 A. Simulate your circuit, and observe the node voltages and branch currents, by clicking on the “V” and “I” buttons on the Capture toolbar. • Submit a printout of your Capture windows showing the values of currents and voltages for both cases (ideal diode and real diode). • List the values of the diode voltage and current for the real diode case, as obtained from SPICE, and compare them with the values obtained in Problem 3, part (b-i).