ECE 3040 Microelectronic Circuits Quiz 7 - Solutions for Problems 1 and 2, Quizzes of Electrical and Electronics Engineering

Download ECE 3040 Microelectronic Circuits Quiz 7 - Solutions for Problems 1 and 2 and more Quizzes Electrical and Electronics Engineering in PDF only on Docsity! ECE 3040 Microelectronic Circuits Quiz 7 June 30, 2004 Professor Leach Name Instructions. Print your name in the space above. The quiz is closed-book and closed-notes. The quiz consists of 2 problems. Honor Code Statement: I have neither given nor received help on this quiz. Initials 1. The BJT has the parameters β = 199 and VBE = 0.65V. It is given that V + = +15V, V − = −15V, R1 = 300 kΩ, and R2 = 33 kΩ. (a) Solve for RE such that IC = 2mA. (b) What is the maximum value that RC can have for the BJT to remain in the active mode? Answers: VBB = V +R2 + V −R1 R1 +R2 = −12.027V RBB = R1kR2 = 29.73 kΩ VBB − V − = IC β RBB + VBE + IC α RE =⇒ RE = α µ VBB − V − − VBE IC − RBB β ¶ = 1007Ω VCB = ¡ V + − ICRC ¢−µVBE + IC α RE + V − ¶ > 0 =⇒ RC = 1 IC · V + − µ VBE + IC α RE + V − ¶¸ < 13.66 kΩ 2. The BJT active mode currents are given by the equations iC = IS0 (1 + vCE/VA) exp (vBE/VT ), iB = iC/β, and β = β0 (1 + vCE/VA). Describe how these equations are used to plot the transfer, output, and input characteristic curves. Show how the parameters gm, r0, and rπ in the hybrid-pi model are defined on the curves. Assume the Q-point values IC , VCE, and VBE. Answers: The plots of the characteristic curves are covered in the class notes. At the Q point, gm is the slope of the transfer characteristic curve, r0 is the reciprocal of the slope of the output characteristic curve, and rπ is the reciprocal of the slope of the input characteristic curve. 1