1 Dalhousie University, Department of Electrical and computer Engineering ECED3201: Introduction to Electronics Fall 2007- Midterm Exam Dr. Kamal El-Sankary Guidelines • Only double-sided one letter size formula sheet is allowed. • Show all your work and reasoning on the exam in order to receive full or partial credit. • Exam Time: 150 minutesProblem 1 - [3 points]:Consider VDD=2.5, v(t)=0.01sint (V), and R=2kin the circuit shown in Fig. 1 Assume that the diode has a 0.7V drop across when the ac signal v(t) is reduced to 0.RVDDv(t)vD(t)iD(t)+-+-+-Fig.1 a. [0.75 pt] Find the dc current, ID, in the diode. b. [0.75 pt] Find the small-signal resistance (ac resistance) of the diode (consider n=2). Assume the diode is at room temperature (VT25mV). c. [1.5 pt] Write mathematical expressions for the total instantaneous current iD(t) and total instantaneous voltage vD(t).Problem 2 - [5 points]:Consider the circuit shown in Fig.2. R1= 10kV1 = 2VvI+-+-V2 = 4VR2= 10k++__vOD1D2Fig.2
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