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EECS 40, Fall, 2004, Midterm 2, White
EECS 40 Midterm Exam II
Fall 2004
Print Name (Last,First) _______________________________________________
Sign Name_________________________________________________________
Do not begin exam until you are instructed to start.
Note that there are several versions of this exam in
the room.
To get credit for a problem, make your method clear to the grader.
Total /
Problem 1 (24 points) General Questions a. [1] Give a concise definition of the properties of an acceptor atom that could be used in a sili- con wafer and explain what it does.
b. [1] What is the power of 50 watts in decibels referred to a reference power of 1mW (this is often referred to as dBm)?
c. [1] Identify clearly the meaning of the acronym rms.
d. [1] What component can you use to couple a time-varying signal to an amplifier yet keep steady currents from flowing into the amplifier? __________________
e. [1] List two components that can form a circuit that acts as a frequency filter. ____________ and _____________.
f. [1] Draw a simple analog circuit that employs negative feedback (make clear where the feed- back appears).
g. [5] List in the table below different devices that are essentially just semiconductor diodes, and indicate their functions:
Table 1: Diodes Name of diode Device
Function of diode device (give distinguishing functions, being as specific as you can)
Problem 2 (16 points) First-Order Transient
In the circuit below, let vA(t) = -1 V for t<0 and vA(t) = 1 V for t>0. R 1 = 2000 Ω, R 2 = 3000 Ω, and C = 10 μF.
a. [2] Find vC(t = 0-).
b. [2] Find vC(t = 0+).
c. [2] Find the current i 1 at t = 0-.
d. [2] Find i 1 (t = 0+).
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e. [4] Find the time constant for this circuit.
d. [4] Find an expression for vC(t) for t>0, and sketch it below
Problem 4 (22 points) Diodes
Each of the diodes in the following circuits is ideal.
a. [6] Find I and V for this circuit (R = 8 kΩ, V+ = +4 V, V- = -3 V)
b. [8] Find I and V for this circuit (R = 3 kΩ, V1 = +1 V, V2 = +3 V, V3 = -3 V) and indicate which diodes are conducting and which are not conducting.
c. [8] The voltage vin in the circuit below is a 1 kHz, 10 V peak-to-peak sine wave. I = 2 mA, V2 = +10 V, R = 1 kΩ. Sketch the waveform resulting at vout and indicate the values of the positive and negative peaks.
c. [2] Identify the terminals of the MOSFET.
d. [4] Draw the load line on the plot and find the Q point (IDQ, VDSQ). IDQ = _________ A VDSQ = _________V
e. [4] Assume that you are considering using this circuit as an analog amplifier and are worried about distortion of the signals. For a positive excursion of vin of 0.5 V how much does vout change (positive or negative)? For a negative excursion of vin of -0.5 V how much does vout change (positive or negative)?
vout for positive excursion of vin: ________V vout for negative excursion of vin: ________V
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g. [4] Draw a simple two-component circuit that represents this MOSFET under the following two extreme conditions:
VGS – VT > 0, VDS < VGS – VT:
VGS – VT < 0:
