HOMEWORK #2
* DUE: WEEK 16, Wednesday (April 29, 1998).
* All problems, figures and page numbers refer to your text Sedra&Smith, 4th Ed.
* Unless noted otherwise, employ the Q2N3904/Q2N3905 BJT's in your simulations.
* Maximum page limit is 10. All pages after that will be ignored!
Consider the common-collector common-emitter cascade amplifier shown in Fig P7.72. Assume that the current sources are ideal (as shown) and the available voltage source is +/- 12 VDC.
(a) Keeping the two bias currents equal (shown as 100uA in the figure), employ a parameter sweep from 1uA to 1000 uA in P-Spice Design Center. Plot Rin, fH, and Vo/Vi with 10 points per decade.
(b) Based on the above results, determine the value of the bias current which maximizes the gain bandwidth product (GBP). (You may use a spread-sheet if that is more convenient for you.)
Note: GBP = fH*(Vo/Vi).
(c) For this value of the bias current, calculate the GBP employing the open-circuit time constants and compare it with the result obtained in part (b).
Problem 2: Comparison of high-frequency response for different configurations:
Consider the amplifier circuits shown in Fig. P7.86. Note that each transistor is biased at 0.5 mA.
(a) Employing P-Spice Design Center determine fH, and Vo/Vs for each configuration.
(b) Identify the configuration with the largest gain bandwidth product (GBP). For this configuration compute the GBP employing the open-circuit time constants and compare to your answer in part (a).
Note: GBP = fH*(Vo/Vs).
Problem 3: Series-series feedback amplifier
(a) Solve problem D*8.33 exactly as stated.
(b) Simulate this circuit with P-Spice Design Center and verify your answer in part (b).
Problem 4: Shunt-series feedback amplifier:
Consider problem P8.42.
(a) Convince yourself that it is so!
(b) Solve problem!
Modified: 2PM, 04/16/1998 by korman@seas.gwu.edu.