Name. Part A (25 Points) Complete on Blackboard. A. (25 Pts) Part B (75 Points) 1. (14 Pts) 2. (4 Pts) 3. (12 Pts) 4. (12 Pts) 5.

Transcription

1 Name Part A (25 Points) Complete on Blackboard A. (25 Pts) Part B (75 Points) 1. (14 Pts) 2. (4 Pts) 3. (12 Pts) 4. (12 Pts) 5. (15 Pts) 6. (15 Pts) 7. (3 Pts) Total Draw circuit diagrams for all problems, especially as you simplify the circuits. Be sure to fully annotate plots, even when the problem does not ask you to do this. Show all of your work At least skim through the entire quiz before you begin and then start with the problems you know best. Note that some questions involve using things you have learned in new ways and some involve some minor new information. Focusing on what you know will make the problems easier to solve. The proctor will only answer clarification questions where wording is unclear or where there may be errors/typos. No other questions will be responded to. K. A. Connor, Revised: 3 December 2015

2 Theme for 2015: Inclusion matters: access and empowerment for people of all abilities The estimated one billion people living with disabilities worldwide face many barriers to inclusion in many key aspects of society. As a result, people with disabilities do not enjoy access to society on an equal basis with others, which includes areas of transportation, employment, and education as well as social and political participation. The right to participate in public life is essential to create stable democracies, active citizenship and reduce inequalities in society. Persons with disabilities must be able to fulfil their role in society and participate on an equal basis with others. It is important to focus on the ability and not on the disability of an individual. Often, the societal image of persons with disabilities is impacted by attitudes based on stigma and discrimination, as well as archaic ideas about disability and persons with disabilities that are often the greatest barrier to their full and equal participation in society and development on an equal basis with others. It is important to note that disability is part of the human condition, and that all of us either are or will become disabled to one degree or another during the course of our lives. By promoting empowerment, real opportunities for people are created. This enhances their own capacities and supports them in setting their own priorities. Empowerment involves investing in people - in jobs, health, nutrition, education, and social protection. When people are empowered they are better prepared to take advantage of opportunities, they become agents of change and can more readily embrace their civic responsibilities. Source: UN.org K. A. Connor, Revised: 3 December 2015

3 Op-Amp Specs (Excerpts) K. A. Connor, Revised: 3 December 2015

4 K. A. Connor, Revised: 3 December 2015

5 K. A. Connor, Revised: 3 December 2015

6 Transformer Specs (Excerpts) Note: This transformer is so good that its single piece price is over $70! K. A. Connor, Revised: 3 December 2015

7 Part B (75 Points) Problem 1 (14 Points) Logic Gates This problem addresses building logic devices from a single type of device, which is shown at the right. a. (3 Pts) What kind of a logic gate is this and what is its truth table? Name the device and fill out the table below. Input A Input B Output b. (3 Pts) Assume that the two inputs are tied together to create a single input device, as shown. Name the device and fill out its truth table below. Input A 0 1 Output c. (4 Pts) Assume that two of the configurations from part b are combined with the device from part a, as shown. Name the device that matches the functionality of this combination and fill out its truth table below. Note that, unlike parts a and b, you are asked to find the values at the intermediate points, not just the inputs and output. C D Input A Input B C D Output K. A. Connor, Revised: 3 December 2015

8 d. (4 Pts) Finally, add one more configuration from part b. Name the device this combination produces and fill out its truth table. Again, you must find the values at intermediate points, not just the inputs and output. C E D Input A Input B C D E Output Q Problem 2 (4 Points) Logical Function What logic gate functionality is described by the following situations? a. You can buy a new car only if both of your parents approve. b. You can buy a new car if at least one of your parents approve. K. A. Connor, Revised: 3 December 2015

9 Problem 3 (12 Points) Operational Amplifiers The two amplifier circuits below are configured with the same op-amp and resistors. Identify Vout which type of amplifier each is and its gain G. For your calculations, assume that R1= Vin 3kΩ and R2 = 12kΩ. a. (4 Pts) The circuit a at the upper left: b. (4 Pts) The circuit b at the upper right: c. (2 Pts) If the op-amp is powered with two 9V batteries, which of the following input voltages listed below will amplifier a (upper left) be able to amplify without distortion? Circle all correct answers. a. 1V b. 2V c. 3V d. 4V e. 5V d. (2 Pts) If the op-amp is powered with two 9V batteries, which of the following input voltages listed below will amplifier b (upper right) be able to amplify without distortion? Circle all correct answers. a. 1V b. 2V c. 3V d. 4V e. 5V K. A. Connor, Revised: 3 December 2015

10 Problem 4 (12 Points) Complex Impedance a) b) Earlier this semester, we analyzed circuits using complex impedances, where the impedance of resistors is real and the impedances of inductors and capacitors are imaginary. The ability to analyze circuits like the ones shown above will be useful in a following problem involving an audio amplifier. To be prepared for the audio problem, you are to evaluate the net impedance of the two circuits at the bottom end (50Hz) and the top end (8.5kHz) of the practical audio range of frequencies. (See Problem 6 for more information.) a. (4 Pts) Evaluate the impedances for both L and C at these two frequencies and fill in the table below. That is, find ZC and ZL. Frequency 50Hz 8.5kHz ZC ZL b. (3 Pts) Find the parallel combination of R and C for both frequencies. c. (3 Pts) Find the series combination of R and L for both frequencies. d. (2 Pts) Simplify your answers to parts b and c by dropping the smaller term, if it is less than 20% of the larger term. K. A. Connor, Revised: 3 December 2015

11 Problem 5 (15 Points) Transformers Transformers also play a role in an interesting circuit you are to analyze in a following problem. Shown at the right is the symbol for an iron core transformer, like the one you built by winding magnet wires on a toroidal ferrite core. Unlike the one you made, this transformer does not have the same number of turns on the primary and the secondary. Rather it has more secondary turns than primary. Assume that the transformer has the load resistor shown (colors are brown-green-yellow). a. (1 Pt) What is the value of the load resistor? Primary 1:10 Secondary b. (2 Pts) What is the ratio of V out? V in c. (2 Pts) What is the ratio of I I out in? d. (3 Pts) What is the input impedance of the loaded transformer Z in? That is, what is V in? I in e. (3 Pts) If the RMS sinusoidal input voltage is 10V, how much power is delivered to the load resistor? f. (4 Pts) The transformer addressed in this problem, is and ideal model of the Jensen audio transformer whose datasheet is provided on page 6 of this quiz. Identify two terms from the datasheet that correspond to the answers to parts b, c or d above. Because this transformer is not ideal (e.g. coupling is not equal to 1), the agreement will not be perfect. However, the values given for the real transformer will be close. K. A. Connor, Revised: 3 December 2015

12 Problem 6 (15 Points) High Quality Microphone Preamplifier Output Impedance of Microphone INPUT AMP-IN 150kΩ The circuit above is an application found in the datasheet for the OP27 op-amp. This figure has been slightly modified to indicate that the 150Ω source is the output impedance of the microphone, which is, otherwise, not shown. This is the practical circuit that the analysis in problems 4 and 5 was done to understand its operation. The typical audio spectra shown below indicate why we chose to analyze the circuits at 50Hz and 8.5kHz, since they nicely cover the useful range of frequencies that a microphone must be sensitive to. K. A. Connor, Revised: 3 December 2015

13 a. (4 Pts) For the audio range of frequencies that you considered in problem 4, you should be able to simplify this circuit by eliminating one component. Identify this component by describing it below and drawing a circle around it in the circuit diagram above. b. (4 Pts) Now that you have simplified the circuit, identify the type of op-amp-based VOUT amplifier it is and determine its gain. V AMP IN c. (4 Pts) From the gain of the amplifier that you just determined and your answer to VOUT problem 7, determine the overall gain of the complete circuit. V IN d. (3 Pts) In the OP27 datasheet, the gain of the overall circuit is given in db, so covert your answer to part c to decibels. K. A. Connor, Revised: 3 December 2015

14 Problem 7 (3 Points) Nest Thermostat Transformer Issue Thermostats with no C-Wire (above) and with C-Wire (below) Problem continues on the next page K. A. Connor, Revised: 3 December 2015

15 One of the great new devices we have to make our homes smart is the Nest thermostat or similar smart devices from other manufacturers. Unfortunately, it is not usually straight-forward to install because the transformers we use to power the thermostats in most of our homes are missing what is called the C-Wire. The two circuit diagrams on the previous page show traditional transformers (above) and transformers for smart thermostats (below). The Bells and Whistles represent the hardware that allows the thermostat to be smart. (3 Pts) Describe what the C-Wire provides for the Bells and Whistles. Any reasonable response is acceptable. Guess if you have to. K. A. Connor, Revised: 3 December 2015