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# final - Fall 2005 6.012 Microelectronic Devices and...

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Unformatted text preview: Fall 2005 6.012 Microelectronic Devices and Circuits Prof. J. A. del Alamo December 19, 2005 - Final Exam Name: Recitation: problem grade 1 2 3 4 total General guidelines (please read carefully before starting): • Make sure to write your name on the space designated above. • Open book : you can use any material you wish. • All answers should be given in the space provided. Please do not turn in any extra material. If you need more space, use the back of the page. • You have three hours to complete your exam. • Make reasonable approximations and state them , i.e. quasi-neutrality, depletion approxima- tion, etc. • Partial credit will be given for setting up problems without calculations. NO credit will be given for answers without reasons. • Use the symbols utilized in class for the various physical parameters, i.e. μ n , I D , E , etc. • Every numerical answer must have the proper units next to it. Points will be subtracted for answers without units or with wrong units. • Use φ = 0 at n o = p o = n i as potential reference. • Use the following fundamental constants and physical parameters for silicon and silicon dioxide at room temperature: n i = 1 × 10 10 cm- 3 kT/q = 0 . 025 V q = 1 . 60 × 10- 19 C s = 1 . 05 × 10- 12 F/cm ox = 3 . 45 × 10- 13 F/cm 1. (28 points) This problem studies an amplifier designed to boost a high-frequency signal midway along a 50-Ω cable. A block diagram of the cable and amplifier is shown below, together with the corresponding circuit. Amplifier 50- Ω cable 50- Ω cable large large large V CC R V EE V EE I 1 I 2 v in R S =50 Ω V CC +- large v out R L =50 Ω +- T1 T2 cable cable In studying the amplifier, make use of the following information: • To avoid undesired reflections within the input and output cables, the amplifier must be designed to have a 50 Ω input resistance and a 50 Ω output resistance. (To learn why, take 6.013!) • The coupling capacitors in the block diagram and circuit isolate the biasing inside the amplifier from the cables. Assume the capacitors are large enough to be short circuits for the purposes of all small-signal modeling. • Assume that both transistors in the amplifier exhibit the same forward current gain β , the same base-emitter capacitance C π , and the same base-collector capacitance C μ . When nu- merical values are needed, let β F = 200, C π = 1 pF, and C μ = 0 . 1 pF. Also, let the thermal voltage V th be 25 mV. For both transistors, ignore their small-signal collector-emitter output resistance until Part 1i)....
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final - Fall 2005 6.012 Microelectronic Devices and...

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