Practice Quiz #3 - Analog Electronics - Fall 2008 | ECE 3050, Quizzes of Electrical and Electronics Engineering

Download Practice Quiz #3 - Analog Electronics - Fall 2008 | ECE 3050 and more Quizzes Electrical and Electronics Engineering in PDF only on Docsity! ECE 3050 Analog Electronics Quiz 3 May 30, 2008 Professor Leach Last Name: First Name: Instructions. Print your name in the spaces above. Place a box around any answer. Equations: gm = IC/VT , rπ = VT/IB, re = VT/IE, r0 = (VA + VCE) /IC , β = β0 (1 + VCE/VA), VT = 0.025V. Honor Code Statement: I have neither given nor received help on this quiz. Initials 1 of 4. The output characteristics of a BJT are shown. What is approximate current gain β at iC = 1.25mA and vCE = 10V? Draw lines and/or points on the graph to show how you obtained your answer. The Q point is just below midway between the IB = 6µA and IB = 8µA lines. To a best estimate, IB = 7.44µA. Thus, β is given by IB ' 7.44µA β ' 1.25mA 7.4µA = 168 2 of 4. A BJT has the parameters β0 = 100, VA = 50V, and VCE = 12V. Calculate IC for rπ = 15kΩ. rπ = VT IB = βVT IC = β0 (1 + VCE/VA)VT IC IC = β0 (1 + VCE/VA)VT rπ = 206.7µA 3 of 4. For the BJT of problem 2, calculate the values of gm and r0. gm = IC VT = 8.267mS r0 = VA + VCE IC = 300 kΩ 4 of 4. For the BJT of problem 2, calculate α and re.α = β 1 + β = 0.994 re = VT IE = αVT IC = 120.3Ω 1