# broadband_analysis_assignment - Problem set Exercises in...

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Problem set: Exercises in nodal analysis, MOTC, and broadband circuits Problem 1 Take a highly simplified model of a bipolar transistor as below Cbe gmVbe B E C Where kT qI g c m / = and f m be g C τ = , and apply it to the amplifier below. Lets assume a transistor with a 500 GHz ft, hence a f τ of 0.32 ps. The bias tees shown have infinite L and C, and the generator, load and termination resistors are 0 Z (e.g. 50 Ohms). Vcc is fairly unimportant, but lets make it 10 volts. amplifier termination termination darlington cell Vcc 10 mA 10 mA generator load Q1 Q2 Vgen Vout Vin a) Using Nodal analysis, calculate the input impedance of the Darlington cell. To simplify the analysis, the input termination and the generator are removed in this calculation. The result should be (i) perhaps surprising and (ii) worrying. By hand, sketch the trajectory of S11 on a smith Chart b) Using hand analysis, compute S21=2Vout/Vgen at mid-band. Use the method of time constants (first-order *and* second order) to compute S21 as a function of frequency. Give values of a1, a2, and (if the 2 poles are real) the 2 pole frequencies or (if the 2 poles are complex) the natural (resonant) frequency and damping factor zeta of the frequency response. c) As verification, simulate the circuit on ADS and generate plots of S11 on a smith chart

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## This note was uploaded on 12/29/2011 for the course ECE 594A taught by Professor Rodwell during the Fall '09 term at UCSB.

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broadband_analysis_assignment - Problem set Exercises in...

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