EE 461G Review Problems for the Final Exam

Print your name. You must show your work to receive partial credit. You may bring a piece of paper with formula, a calculator, a ruler, a pencil, and an eraser.

Problem 1 Draw the small-signal models for BJT and FET including both DC and AC components. Label components, current, and voltage.

Problem 2 Approximately draw transfer characteristics of circuits (a) and (b) separately and their output voltage in the space below. Point out which one is a rectifier and which one is a clipping circuit? (Vf=0.7V)

Transfer characteristics for (a) Vout for (a)

Transfer characteristics for (b) Vout for (b)

Problem 3 A bipolar junction transistor amplifier with a incremental signal gain bo of 100 is shown below. (a) What type of the DC bias does this circuit have? (b) Find the DC voltage VB from the base B to the ground; (c) The ac signal voltage vb from the base B to the ground; (d) the output ac signal vout.

Problem 4 An n-channel enhancement-mode MOSFET is connected to the circuit as shown below. The I-V characteristic of the transistor is also shown below. (VTR=1V)

(a) Write the equation for the load line and draw the load line on the I-V curves to find the operating point A. What is the operating region?

(b) If RL=0.4 kW is connected to the output (or D and S), write the equation for the load line and draw the load line on the I-V curves to find the operating point B. What is the operating region?

Problem 5 An n-channel enhancement-mode MOSFET is connected to the circuit as shown below. (VTR=1V) The I-V curves are shown below.

(a) Using the MOSFET model and the I-V curves below to calculate K approximately.

(b) Using the results in Problem 4 (a) to find the transconductance gm.