## ELEC 2000 Semiconductor Devices Homework #1 Choose the answer that best completes the statement or answers the question. (1) Assume the valence electron is removed from a copper atom. The net charge of the atom becomes a. 0 b. +1 c. -1 d. +4 (2) The valence electron of a copper atom experiences what kind of attraction toward the nucleus? a. None b. Weak c. Strong d. Impossible to say (3) How many valence electrons does a silicon atom have? a. 0 b. 1 c. 2 d. 4 (4) Silicon atoms combine into an orderly pattern called a a. Covalent bond b. Crystal c. Semiconductor d. Valence orbit (5) An intrinsic semiconductor has some holes in it at room temperature. What causes these holes? a. Doping b. Free electrons c. Thermal energy d. Valence electrons (6) The merging of a free electron and a hole is called a. Covalent bonding b. Lifetime c. Recombination d. Thermal energy (7) At room temperature an intrinsic silicon crystal acts approximately a. A Battery b. A conductor c. An insulator d. Copper wire (8) The amount of time between the creation of a hole and its disappearance is called a. Doping b. Lifetime c. Recombination d. Valence (9) A conductor has how many type of flow? a. 1 b. 2 c. 3 d. 4 (10) A semiconductor has how many types of flow? a. 1 b. 2 c. 3 d. 4 (11) For semiconductor material, its valence orbit is saturated when it contains a. 1 electron b. Equal (+) and (-) ions c. 4 electrons d. 8 electrons (12) In an intrinsic semiconductor, the number of holes a. Equal the number of free electrons b. Is greater than the number of free electrons c. Is less than the number of free electrons d. None of the above (13) The number of free electrons and holes in an intrinsic semiconductor decreases when the temperature a. Decreases b. Increases c. Stays the same d. None of the above (14) The flow of valence electrons to the right means that holes are flowing to the a. Left b. Right c. Either way d. None of the above (15) Holes act like a. Atoms b. Crystals c. Negative charges d. Positive charges (16) An donor atom has how many valence electrons? a. 1 b. 3 c. 4 d. 5 (17) If you wanted to produce a p-type semiconductor, which of these would you use? a. Acceptor atoms b. Donor atoms c. Pentavalent impurity d. Silicon (18) Electrons are the minority carriers in which type of semiconductor? a. Extrinsic b. Intrinsic c. n-Type d. p-type (19) Silver is the best conductor. How many valence electrons do you think it has? a. 1 b. 4 c. 18 d. 29 (20) Which of the following describes an n-type semiconductor? a. Neutral b. Positively charged c. Negatively charged d. has many holes (21) What is the barrier potential of a silicon diode a room temperature? a. 0.3 V b. 0.7 V c. 1 V d. 2 mV per degree Celsius

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## ENGR 2010 (Section 02) – Assignment 7 Due: Wednesday November 25th, 11:59 pm Points: 20 Prof. Lei Reading: Sections 6.2-6.3 of Nilsson and Riedel, Electric Circuits, 9th Edition Submit electronic solutions (i.e. using Microsoft Word or a scanned copy of your written work) to the following problems on Blackboard. To receive credit, you must show work indicating how you arrived at each final answer. Problem 1 Consider the RC circuit on the right. and suppose that Vs(t) is a time-varying voltage input shown at the bottom. a) Suppose VC(0) = 0V. Plot VR(t) and VC(t) from 0ms to 300ms. Show your work in obtaining VR(t) and VC(t). b) Suppose the capacitance value is changed to 2μF, and VC(0) = 0V. Plot VR(t) and VC(t) from 0ms to 300ms. Show your work in obtaining VR(t) and VC(t). c) Explain how VC(t) qualitatively compares with Vs(t), and how VR(t) qualitatively compares with Vs(t). d) Explain how the capacitance value affects VC(t). t Vs(t) 1V -1V 50ms 100ms 150ms 200ms 250ms + – Vs(t) 100000 Ohms 1 uF + – VC(t) + – VR(t) 0ms 300ms Note: Capacitors are often used to protect against sudden changes in a voltage value, which could damage electronic components. Here, Vs(t) undergoes many sudden changes, but VC(t) undergoes less change. Problem 2 Using PSpice, perform two transient analysis simulations – one for the circuit in part (a), and one for the circuit in part(b) of problem 1 – to verify that your plots in problem 1 are correct. For each simulation, plot the traces for VR(t) and VC(t). Hint: You may need to perform arithmetic operations between simulation traces. Take a screenshot of your constructed circuits and the simulation traces for VR(t) and VC(t), which you will submit onto Blackboard. t Vs(t) 1V -1V 50ms 100ms 150ms 200ms 250ms + – Vs(t) 100000 Ohms 1 uF + – VC(t) + – VR(t) 0ms 300ms 1 uF or 2 uF Problem 3 Consider the Resistor-Diode circuit on the right, and suppose that Vs(t) is a time-varying voltage input shown at the bottom. Suppose that for the diode to turn on, it needs 0.7V between the positive and negative terminals. a) Plot VR(t) and VD(t) from 0ms to 300ms b) Explain how VD(t) qualitatively compares with Vs(t), and how VR(t) qualitatively compares with Vs(t). t Vs(t) 1V -1V 50ms 100ms 0ms 150ms 200ms 250ms 300ms + – Vs(t) 100000 Ohms + – VD(t) + – VR(t) Problem 4 Using PSpice, perform a transient analysis simulation for the circuit in problem 3 – to verify that your plots in problem 3 are correct. For the simulation, plot the traces for VR(t) and VD(t). To create the diode in PSpice, use the Dbreak component. After placing the component on the page, highlight the component, and edit the Pspice model (Edit -> PSpice Model) and set Rs to 0. Hint: You may need to perform arithmetic operations between simulation traces. Take a screenshot of your constructed circuit and the simulation traces for VR(t) and VD(t), which you will submit onto Blackboard. Note that your simulation trace plots may not be exactly the same as those from Problem 3, since the PSpice diode model has a turn-on voltage that’s not exactly 0.7V. t Vs(t) 1V -1V 50ms 100ms 0ms 150ms 200ms 250ms 300ms + – Vs(t) 100000 Ohms + – VD(t) + – VR(t) Problem 5 (Bonus: 5 points) In the circuit from problem 1 (shown on the right), write several sentences to explain why VC(t) is often referred to as the “low-pass filtered” output, and VR(t) is often referred to as the “high-pass filtered” output. You will need to look up the definitions for “low-pass” and “high-pass” filters. Examining your plots for VC(t) and VR(t) will help. t Vs(t) 1V -1V 50ms 100ms 150ms 200ms 250ms + – Vs(t) 100000 Ohms 1 uF + – VC(t) + – VR(t) 0ms 300ms

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## Problem 6.15 The boost converter of Fig 6-6 has the following parameters: Vs=20V, D=0.6, R=12.5Ω, L=65μH, C=200μF, and switching frequency = 40kHz. a. Determine the output voltage. b. Determine the average, maximum, and minimum inductor current. c. Determine the output voltage ripple. d. Dermine the average current in the diode.

## Problem 6.7 A buck converter has an input of 60V and an output fo 25V. The load resistor is 9Ω, the switching frequency is 20-kHz, L=1mH, and C=200μF. a. Determine the duty ratio. b. Determine the average, peak, and rms inductor current. c. Determine the average source current. d. Determine the peak and average diode current.

## Biomedical Signal and Image Processing (4800_420_001) Assigned on September 12th, 2017 Assignment 4 – Noise and Correlation 1. If a signal is measured as 2.5 V and the noise is 28 mV (28 × 10−3 V), what is the SNR in dB? 2. A single sinusoidal signal is found with some noise. If the RMS value of the noise is 0.5 V and the SNR is 10 dB, what is the RMS amplitude of the sinusoid? 3. The file signal_noise.mat contains a variable x that consists of a 1.0-V peak sinusoidal signal buried in noise. What is the SNR for this signal and noise? Assume that the noise RMS is much greater than the signal RMS. Note: “signal_noise.mat” and other files used in these assignments can be downloaded from the content area of Brightspace, within the “Data Files for Exercises” folder. These files can be opened in Matlab by copying into the active folder and double-clicking on the file or using the Matlab load command using the format: load(‘signal_noise.mat’). To discover the variables within the files use the Matlab who command. 4. An 8-bit ADC converter that has an input range of ±5 V is used to convert a signal that ranges between ±2 V. What is the SNR of the input if the input noise equals the quantization noise of the converter? Hint: Refer to Equation below to find the quantization noise: 5. The file filter1.mat contains the spectrum of a fourth-order lowpass filter as variable x in dB. The file also contains the corresponding frequencies of x in variable freq. Plot the spectrum of this filter both as dB versus log frequency and as linear amplitude versus linear frequency. The frequency axis should range between 10 and 400 Hz in both plots. Hint: Use Equation below to convert: Biomedical Signal and Image Processing (4800_420_001) Assigned on September 12th, 2017 6. Generate one cycle of the square wave similar to the one shown below in a 500-point MATLAB array. Determine the RMS value of this waveform. [Hint: When you take the square of the data array, be sure to use a period before the up arrow so that MATLAB does the squaring point-by-point (i.e., x.^2).]. 7. A resistor produces 10 μV noise (i.e., 10 × 10−6 V noise) when the room temperature is 310 K and the bandwidth is 1 kHz (i.e., 1000 Hz). What current noise would be produced by this resistor? 8. A 3-ma current flows through both a diode (i.e., a semiconductor) and a 20,000-Ω (i.e., 20-kΩ) resistor. What is the net current noise, in? Assume a bandwidth of 1 kHz (i.e., 1 × 103 Hz). Which of the two components is responsible for producing the most noise? 9. Determine if the two signals, x and y, in file correl1.mat are correlated by checking the angle between them. 10. Modify the approach used in Practice Problem 3 to find the angle between short signals: Do not attempt to plot these vectors as it would require a 6-dimensional plot!

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