課程名稱︰電子學一
課程性質︰必修
課程教師︰吳肇欣
開課學院：電資學院
開課系所︰電機系
考試日期（年月日）︰2014/11/13
考試時限（分鐘）：110
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1. Fig.1 shows the circuit model of a voltage amplifier loaded with a resistor
RL and a capacitor CL. The parameters are given as RS = 40 kΩ, Ri = 200kΩ,
AVo = 140, and Ro = 2kΩ.
(1)[7%] Find the minimum RL allowed to maintain a voltage gain no less than
40dB.
(2)[7%] Base on (1), what is the maximum CL allowed to keep a 3-dB frequency
higher than 20 kHz?
(3)[9%] The input voltage form is given by 0.1sin(10^4t) + 0.5sin(10^5t)[V].
With the minimum RL and the maximum CL, find the output voltage Vo.
-----Fig.1 http://imgur.com/T23BVls
2. Differential amplifiers are one of the most important circuit block in
analog circuits. For the following two kinds of differential amplifier
please determine their differential gain, differential input resistance,
and common-mode gain. Assume ideal operational amplifier.
(1)[12%] In Fig.2. Note: R1, R2, R3, and R4 are different resistors.
(2)[12%] In Fig.3. Note: R1 = R2 = R3 = R4 = R5 = R6 = 10k
-----Fig.2 http://imgur.com/D92j5KV
-----Fig.3 http://imgur.com/dkYSrRR
3.[10%] True or False. Correct the statements if they are wrong. Credits will
be given only when you correct it right.
(1) In thermal equilibrium, the intrinsic concentration of Silicon(EG = 1.1eV)
is smaller than that of Germanium(EG = 0.67eV) at room temperature.
(2) In thermal equilibrium, n-type silicon semiconductor is negatively-charged
and p-type silicon semiconductor is positively-charged at room
temperature.
(3) In thermal equilibrium, the built-in voltage cannot be measured by a
potential meter applied on the external terminals of the pn junction.
(4) In thermal equilibrium, extrinsic silicon semiconductor shows larger
electrical resistivity than intrinsic silicon semiconductor does at room
temperature.
(5) In thermal equilibrium, there is no current going on in the pn junction
when the external terminals are left open-circuited.
(6) The depletion region in the p-side will be larger than that in the n-side
if the n-type doping is smaller than the p-type doping in the pn junction.
(7) When the pn junction is forward-biased, the forward conducting current
can be formed by holes drifting from p-side to n-side and electrons
drifting from n-side to p-side, depending on the values of applied voltage
and electrical field.
(8) The charge-storage effects in the pn junction can be modeled by junction
capacitance in reverse bias and diffusion capacitance in forward bias.
(9) The excess concentration of minority carriers in the pn junction under
forward bias will decay with distance linearly due to the recombination
process with majority carriers.
(10)The avalanche breakdown occurs when the majority carriers that cross the
depletion region under the influence of the electric field gains
sufficient kinetic energy to be able to break covalent bonds in atoms
with which they collide.
4.[13%]Consider an OP connecting in Fig. 4. The input waveform is a continuous
pulse with period of 100μs, as shown in Fig. 5. Assuming that R1 =
1kΩ, R2 = 4kΩ, and the cut-off frequency ft of the OP is 200kHz and
slew rate is 0.5V/μs. Please draw the otput waveform Vo(t) with time.
Label correctly the detailed information of the output waveform in your
plot, i.e. voltage and time at every corner/turning point.
-----Fig.4 http://imgur.com/RMI6EgX
-----Fig.5 http://imgur.com/ytNhtrR
5.[10%]In the capacitor-coupled attenuator circuit shown in Fig.6, I is a dc
current that varies from 0 mA to 1 mA, D1 and D2 are diodes with n=1,
and C1 and C2 are large coupling capacitors. For very small input
signals, find the values of the ratio Vo/Vi for I = 0μA, 100μA,
500μA, 900μA, and 1mA.
-----Fig.6 http://imgur.com/o3zBy4e
6.[4%]A shunt regulator utilizes a zener diode whose voltage is 5V at a
current of 50 mA and whose incremental resistance is 5Ω. The diode is
fed from a supply of 15-V nominal voltage through a 150-Ω resistor.
What is the output voltage at no load?
[6%]Find the line regulation and load regulation.
7.[3%]A full-wave bridge rectifier circuit with a 1.5-kΩ load operates from
a 100-V (rms) 60-Hz household supply through a 10-to-1 step-down
transformer having a single secondary winding. It uses four diodes, each
of which can be modeled to have a 0.7V drop for any current. What is the
peak value of the rectified voltage accross the load?
[4%]For what fraction of a cycle does each diode conduct?
[3%]What is the average current through the load?
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※ 編輯: WhyThe (140.112.243.10), 11/13/2014 23:30:58