(Due Friday, Feb 11th)
E.E. 325b/985b
Peter J. Kindlmann
Spring 2000
This problem will build on your earlier familiarization sessions using Electronic WorkBench (EWB).
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(a) Do Sedra & Smith, prob. 3.70 on paper except use as the Q-points four bias currents, 1mA, 0.1mA, 10uA and 1uA. Then, arrive at attenuation values using EWB simulation and a 1N914 diode. Investigate and explain the differences. Use the modified schematic below to do the simulation, using a 1kHz input signal.
(b) Again for the four Q-points and a 1N914 diode, use EWB to decide what input amplitude vin(t) can be applied for the output vo(t) to have less than 3% total harmonic distortion (THD). (Assume large values for C.)
(c) Now use one of the symmetrical two-diode forms of attenuator we developed in class (you decide which one). For the same attenuations corresponding to the four Q-points above, and the same input amplitudes, what is the THD now? Why is it different?
(d) Finally, use the four-diode bridge attenuator, the last configuration we explored in class, which reverses the roles of the series and shunt elements of the attenuator-the diodes are now the series element. Use C2=10uF and R2=1k, and eliminate R1 and C1. Use the same four Q-points. For the same values of THD as in (c) at equivalent attenuations, what input amplitudes can be applied? Compare the relative merits of (c) and (d).