课程名称︰电子学 课程性质︰选修 课程教师︰李佳翰 开课学院：工学院 开课系所︰工科海洋系 考试日期（年月日）︰2010/04/12 考试时限（分钟）：180min 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Note: Write your name and student ID in the above and answer sheet. The question sheet should return with your answer sheet. There are total 110 points. If you get more than 100 points, you get 100 points for the exam grade. The grading will be posted on NTU CEIBA, and you can contact TA or instructor if you have any question about your grade. Prob.1 (34%) Fig.(a) shows a pn junction diode. This pn junction has the drift current Is and diffusion current Id. Notice that xp > xn in the figure, which is different as the figure in the textbook. (a) What are the minority carriers in p-type silicon? (1%) (b) What are the minority carriers in n-type silicon? (1%) (c) What is the drift current? Which direction does it flow in Fig.(a)? (2%) (d) What is the diffusion current? Which direction does it flow in Fig.(a)?(2%) (e) What is the minority-carrier lifetime? (1%) (f) With no applied voltage in pn junction, is the drift current or diffusion current larger? (1%) (g) If this pn junction is applied from no voltage to reverse-bias voltage, is the drift current or diffusion current larger? Does the depletion region get wider, narrower or unchanged? (2%) (h) If this pn junction is applied from no voltage to forward-bias voltage, is the drift currnet or diffusion current larger? Does the depletion region get wider, narrower or unchanged? (2%) (i) What is the depletion capacitance? (1%) (j) What is the diffusion capacitance? (1%) (k) Describe the two breakdown mechanism, zener breakdown and avalanche breakdown. (2%) (l) According to Fig.(a), plot the carrier concentration p and n, change density Nd and Na, electric field, and electric potential as a function of x. (8%) (m) If n region is heavily doped than the p region, i.e., Nd > Na, plot the minority-carrier distribution and the depletion region in a forward-biased pn junction. (7%) (n) Find Ip and In as the diode is conducting a forward current I=1mA with Na=10^16/cm^3, Nd=10^18/cm^3, Lp=5μm, Ln=10μm, Dp=10cm^2/s, Dn=20cm^2/s. (2%) (o) Fig.(b) shows the curves for temperature dependence of the diode forward characteristic. Which one, Ta or Tb, is higher temperature? (1%) ┌───────┬─────────┬──────┬───────┐ │ Holes │╭─╮╭─╮╭─╮│╭─╮╭─╮│Free electrons│ │＋＋＋＋＋＋＋││－││－││－│││＋││＋││－－－－－－－│ │＋＋＋＋＋＋＋│╰─╯╰─╯╰─╯│╰─╯╰─╯│－－－－－－－│ │＋＋＋＋＋＋＋│╭─╮╭─╮╭─╮│╭─╮╭─╮│－－－－－－－│ │＋＋＋ｐ＋＋＋││－││－││－│││＋││＋││－－－ｎ－－－│ │＋＋＋＋＋＋＋│╰─╯╰─╯╰─╯│╰─╯╰─╯│－－－－－－－│ │＋＋＋＋＋＋＋│╭─╮╭─╮╭─╮│╭─╮╭─╮│－－－－－－－│ │＋＋＋＋＋＋＋││－││－││－│││＋││＋││－－－－－－－│ │＋＋＋＋＋＋＋│╰─╯╰─╯╰─╯│╰─╯╰─╯│－－－－－－－│ └───────┴─────────┴──────┴───────┘ ────┼─────────┼──────┼─────→ x -xp 0 xn Fig.(a) i ↑ │ Ta Tb │ │ │ │ │ 　　│ │ │ 　　│ │ │ 　　│ │ /　　　/ │　　　／　　 ／ └──────────→v Fig.(b) Prob.2 (10%) The circuit in the figure utilizes three identical diodes aving n=1 and Is=10^-14 A. (1) Find the value of the current I required to obtain an output voltage Vo=2V. (5%) (2) If a current of 1mA is drawn away from the output terminal by a load, what is the change in outpot voltage? (5%) Hint: use exponential model for the diode forward characteristic. ↑ ╭┴╮ │↓│I ╰┬╯ ├──→ Vo │ ▽ │ ▽ │ ▽ ps:请将三角形视为diode..XD │ ≡ Prob.3 (10%) (1) Write the full name of MOSFET in English. (6%) (2) Write the full name of BJT in English. (3%) (3) Which one is most widely used in electronic devices, especially in the design of integrated circuits(ICs)? (1%) Prob.4 (6%) Which are the circuit symbols for NMOS? S D S │ │ │ │├─┘ │├─┘ │├←┘ G─┤├─→B G─┤│ G─┤│ │├─┐ │├→┐ │├─┐ │ │ │ D S D (a) (b) (c) S D D │ │ │ │├←┘ │├─┘ │├─┘ G─┤├──B G─┤├─→B G─┤├←─B │├─┐ │├→┐ │├─┐ │ │ │ D S S (d) (e) (f) Prob.5 (20%) Figures (a) to (d) are the same figures of the cross-section of an enhancement- type MOSFET. (a) Is this NMOS transistor PMOS transistor in Fig.(a)? (2%) (b) Apply the voltages in drain, source and gate and ground the body, we get the Id-Vsd characteristics as shown in Fig.(e). For operating point A, B, C, D in Fig.(e), please plot the depletion region and the channel in Fig.(a),(b),(c),(d), separately. (12%) (c) If this transistor is operated in the case with |Vt|=1V, |Va|=50V, |Vgs|=3V |Vds|=4V and kp'W/L = 1mA/V^2, which is this case in Fig.(e)? (3%) (d) Find Id in (c). (3%) 　　Ｄ　　　Ｇ　　　Ｓ │ │ │ │ │ │ ┌┬╧┬─═╧═─┬╧┬┐ Fig.(a)~(d) ││p+│ │p+││ 都是相同的图(右图) │╰─╯ ╰─╯│ │ │ │ n-type substate │ └────═╤═────┘ │ Ｂ Id↑ triode saturation _,-' Vsg + Vt = 2.0V │ | 　　　　　　_,-' │ | _,-' │ / _,-' │ | _,-' __- Vsg + Vt = 1.5V │ /_,-' __,--' │ _,-' __,--' ↖slope = 1/r0 │ ／ | __,C-' │ B _/_,--' │/ ／/ 　　　　　　　　_____,,,, Vsg + Vt = 1.0V (四条斜线的延伸 │| /_/____,,,,,-----''''' 　　会在x轴上　　 　　│|///____________________________ Vsg + Vt = 0.5V 　　交於-Va这个点)　　│||/ ───────────┴D─────────A─────────→ Vsd -Va ↗ ↖ Point D is Vs=Vg=Vd=0 Vsg + Vt ≦ 0V 　　　　　　　　　　　　　　　　　Fig.(e) Prob.6 (18%) Below figure shows a pnp transistor biased to operate in the active mode. (1) Please write what happen in the blank? (15%) (2) Which one (emitter, base, or collector) has the heavy doping? (3%) Forward-biased Reverse-biased ╓────────┼─┬───────┬─┼────────╖ ║ ｐ └→│ ｎ │←┘ ｐ ║ ║ ╭ │ │ ╮ ║ Ie ║ │ ▇▇▇▇▇▇ │ ▇▇▇▇▇ │ ▇▇▇▇▇ ＞├Ic║ Ic → ║ │▇▇▇▇▇▇▇▇│▇▇▇█▇▇▇│▇▇▇▇▇▇▇ ╯ ║ → ┌─○─╢Ie┤ │ ▽Ib2 ←┼────┐ ╟─○─┐ │ Ｅ ║ │＜ ▇▇▇▇▇ │ Ib1 │ ▇▇▇▇ ║ Ｃ │ │ ║ │ ▇▇▇▇▇▇ │ ╰─┬─╯ │ ▇▇▇▇▇▇ ║ │ │ ║ ╰　　　　　　　　│ Ib │ ║ │ │ ╙──────────┴──═╤═──┴──────────╜ │ │ │ │ │ + - │↓Ib + - │ ├─────○ Veb ○────────┼───────○ Vbc ○──────┤ │ │ │ │↑Ie ○Ｂ Ic│ ││ Ie │ Ic ↓│ │ ←─ │ ←─ │ └────∥─────────────┴─────────────∥────┘ Veb Vbc Prob.7 (12%) For each of the circuits shown below, find the emitter, base, and collector voltages and currents. Use β=30, but assume |Vbe|=0.7V independent of current level. +3V +3V +3V +3V ↑ ↑ ↑ ↑ ︴2.2kΩ ︴1kΩ ︴1.1kΩ ︴1kΩ │ │ +3V │ +3V │ ／ ↙ ↑ ↙ ↑ ／ ┌─┤ Q1 ┌─┤ Q2 └─┤ Q3 └─┤ Q4 ≡ ↘ ≡ ＼ ＼ ↘ │ │ │ │ ︴2.2kΩ ︴1kΩ ︴560Ω ︴470Ω │ │ │ │ ↓ ↓ │ │ -3V -3V ≡ ≡ (a) (b) (c) (d) (Q1~Q4为四个BJT，其他条件如图所示) --

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