課程名稱︰電子學一
課程性質︰系必修
課程教師︰呂良鴻 林浩雄 李泰成
開課學院：電資學院
開課系所︰電機系
考試日期（年月日）︰96/11/22
考試時限（分鐘）：140分鐘
是否需發放獎勵金：是 謝謝
（如未明確表示，則不予發放）
試題 :
1. (1) Explain briefly how a depletion region is formed at the
interface of a p-n junction. (5pts)
(2) Explain the origins of diffusion capacitance and depletion
capacitance in a p-n junction. (5pts)
2. For an integrator as shown in Fig.1, derive Vout(s)/Vin(s)
if the gain of the op amp is finite, let's say Ao.
Compared with an ideal integrator (gain of the op amp is finite),
please describe the difference in frequency domain. (8pts)
C
┌────┤├────┐
│ │
R │ ｜╲ │
Vin ─﹋﹋﹋─┴──｜－╲ │
｜ ╲ ｜
｜ ﹥───┴──Vout
│ ╱
┌──｜＋╱
│ ｜╱
│
接地
Fig. 1. Circuit of the integrator
3. (a) Assumeing the op is ideal, find Av (=Vo/Vi), Ri and Ro of the
circuit in Fig. 2(a). (10pts)
(b) Assuming the open-loop gain of the op is Avo, find Av, Ri and Ro
of the circuit in Fig. 2(a). (10pts)
(c) Assuming the op is ideal, find the Av, Ri and Ro of the circuit
in Fig. 2(b). (10pts)
R R
┌────﹋﹋﹋─┬─﹋﹋﹋──┐
│ │ │
R │ ｜╲ ︴ 接地
Vi ─﹋﹋﹋─┴──｜－╲ ︴R
｜ ╲ ｜
｜ ﹥─┴─── Vo
│ ╱
┌──｜＋╱
│ ｜╱
接地
Fig. 2(a).
R R
┌────﹋﹋﹋────┬─﹋﹋﹋──┐
│ │ │
R │ ｜╲ ︴ 接地
┌──﹋﹋﹋─┴──｜－╲ ︴R
接地 ｜ ╲ ｜
｜ ﹥─﹋﹋﹋┴── Vo
R │ ╱
Vi ──﹋﹋﹋──｜＋╱
｜╱
Fig. 2(b).
4. The I-V characteristic of a NMOSFET in the triode region is
Id = kn' (W/L) [(Vgs-Vt)Vds - 0.5 Vds^2].
If this device is then pinched-off, derive the I-V equation.
What is pinch-off? Write down the condition of pinch-off in
terms of the voltage of the transistor. Draw the large-signal
equivalent-circuit model of this device in saturation region
(pinched-off). (10pts)
5. Fig. 3 shows a shunt regulator using a Zener diode whose model
is also shown in the figure. Assume the supply voltage Vs can
vary by ±ΔVs. Find the line regulation ΔVo/ΔVs. (10pts)
↑
│ Vs±ΔVs
│ ｜
︴R ─┴─
︴ │ ┬ Vzn
├─────┬── Vo±ΔVo ╴╴/ ｜
│ │ Zener/╱╲ ≡ ︴
╴╴/ ｜ ￣￣ ︴Rz
Zener/╱╲ ︴Rl ｜ ｜
￣￣ ︴
｜ ｜ Model of the Zener diode
接地 接地
Fig. 3.
6. The following circuit contains two diode Da and Db. Note that
Is = 10^-15 A for both diode and Vt = kT/q = 25mV.
(a) Use constant-voltage-drop diode model to estimate Vout,
if Va = 2 Volt, and Vb = 1 Volt. (2pts)
(b) Use exponential current to calculate Vout, if Va = Vb = 2 Volt.
Note that the error tolerance should be less than 1 mV. (6pts)
(c) Now, if Va =(2 +ΔV) Volt, and Vb =(2 －ΔV) Volt, and what's
the change of Vout compare with the result in part (b)? (4pts)
(d) Now repeat part(c) if ΔV is large, what ΔV can make
Ida/Idb = 100 ? Also, calculate the corresponding Vout. Under
this condition, we can say Da is ON and Db is OFF. (10pts)
5 Volt
│
︴
︴1kΩ
│
┌────┴───┬── Vout
│ │
╴╴ ╴╴
Da ╲╱ ╲╱ Db
￣￣ ￣￣
｜ ｜
│ │
Va Vb
Fig. 4.
7. For the circuit shown in Fig. 5, both diodes are identical,
conducting 10mA at 0.7V and 100mA at 0.8V. Find the value
of R for which V = 100mV. (10pts)
↑
│
╭─╮ I
│↓│10mA
╰─╯
│
├────────┐
│ │
╴╴ ╴╴
D2 ╲╱ ╲╱ D1
￣￣ ￣￣
｜ ｜
│ ├────。
接地 ︴ ＋
︴R
│ V
│ －
接地
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