课程名称︰数位电子与数位电路 课程性质︰必修 课程教师︰赖飞罴 开课学院：电资学院 开课系所︰资工系 考试日期（年月日）︰2011.11.10 考试时限（分钟）：100分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题： 1. Please find Thevenin and Norton equivalent circuits for the network in Fig.1 and explain what is the advantage of source transformation in detail. (30pts) 3Ω 3Ω a ┌──﹏﹏﹏──┬─────┬───﹏﹏﹏──○ │ │ │ │ │+ │ ╱╲ ︴ ╱╲ ╱ ＋ ╲ 6Ω ︴V_a ╱ │ ╲ 3A ╲ － ╱ ︴ ╲ ↓ ╱ ╲╱ 2V_a │- ╲╱ │ │ │ │ │ │ b └───────┴─────┼────────○ ─┴─ ￣ Fig.1：http://i.imgur.com/BSFFn.jpg 2. A simple electronic thermometer based on the circuit shown as Fig.2 in which 2 identical diodes are biased by current source I_1 and I_2. This simple but elegant circuit forms the heart of most of today's highly accurate electronic thermometers. Please try to explain in detail that why we prefer differential to single-ended. (15pts) +V_cc ○ │ ┌────┴────┐ │ │ I_1 ╱╲ ╱╲ I_2 ╱ │ ╲ ╱ │ ╲ ╲ ↓ ╱ ╲ ↓ ╱ ╲╱ ╲╱ │ + - │ ├─○ V_PTAT ○─┤ │ + + │ ┌┴┐ ┌┴┐ D1 ╲╱ V_D1 V_D2 ╲╱ D2 ─┼─ ─┼─ │ - - │ └────┬────┘ ─┴─ ￣ Fig.2：http://i.imgur.com/ZRGUj.jpg 3. Please find the Q-point for the 3 diodes in Fig.3. Use the constant voltage drop model with V_on = 0.6V for the diodes. (15pts) +10V ○ │ ︴ R_1 ︴10kΩ ︴ D1 _ │ _ D2 D3 _ A │ ╱│ ↓I_1 │╲ │ C │ ╱│ ┌──┼◇ ├──┴──┤ ◇┼──┬──┼◇ ├──┐ I_2↓ │ ╲│ B │╱ │ ↓I_3 │ ╲│ │ │ ￣ ￣ │ ￣ ─┴─ ︴ ︴ ￣ R_2 ︴10kΩ R_3 ︴10kΩ ︴ ︴ │ │ ○ ○ -20V -10V Fig.3：http://i.imgur.com/BEVQz.jpg 4. (l) Please indicate the course teacher's name in Chinese. (5pts) (2) P|ease indicate the name of textbook and author(s). (5pts) 5. Please try to describe how to measure electronic charge in detail. (20pts) Q_e = -1.6 x l0^(-l9) Coulomb 6. (1) Fig.4 gives the electron and hole concentrations in a 2-μm-wide region of silicon. In addition, there is a constant electric field of 10^3 V/m present in the sample. What is the total current density at x = 0 ? What are the individual drift and diffusion components of the hole and electron current densities at x = lμm ? Assume that the electron and hole mobilities are 350 and 150 cm^2/V*s , respectively. (15pts) E ←─── ▕ ▏ 1.01*10^18▕╲ ▏ ▕ ╲p(x) ▏ ▕ ╲ ▏ 10^16 ▕╲ ╲ ▏ ▕ ╲ ╲▏ ▕ ╲ ▏10^18 ▕ n(x)╲ ▏ ▕ ╲▏ ▕ ▏10^4 ▕ ▏ x=0 x=2μm Fig.4：http://i.imgur.com/FgII2.jpg (2) A 10-μm-long block of p-type silicon has an acceptor doping profile given by N_A(x) = 10^14 + (10^8)exp(-10^4 x) , where x is measured in cm. Please try to demonstrate that the material must have a nonzero internal electric field E. What the value of E at x = 0 ? (15pts) --

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