ENGR 072 - Electronic Circuit Applications,
Fall 2019


Course information

Instructor: Erik Cheever, Singer 236, 610-328-8076, echeeve1@swarthmore.edu, calendar
Meeting time & place: MWF 11:30-12:20, Singer 346
Lab time & place: Lab is in Singer 246 and is self scheduled.  I will be available at least one afternoon (TBD) per week (check my schedule)
Text:
  1. Microelectronics Circuits, 6e, by Sedra and Smith, Oxford University Press
    This is an older edition of the textbook, and we will only be using a few chapters. You should be able to get it more cheaply than the most current edition (note that is is the 6th edition), but since it is an older edition the bookstore won't carry it. Amazon link.
  2. Useful refence, but there is no need to purchase: Op Amps for Everyone, available online (expanded print copy is also available on Amazon - the online version is sufficient for this class).
OneNote: link - lectures
Files: link - directory for solutions, class handouts...
Moodle: https://moodle.swarthmore.edu/course/view.php?id=15955
Meeting with me: Check my schedule for office hours (I will try hard to be available then), but feel free to drop by anytime I am in my office. If you are having trouble finding me, email is probably the best way to contact me..



Assignments

Homework due dates will be on the course moodle page; assignments will be turned in on moodle as a single pdf. Late homework will be penalized 25%, and won't be graded after 1 week.

We will go over any questions on the homework the day before it is due (assignments are due Thursday unless otherwise specified). If your initials are next to the problem, you are responsible for presenting an outline to the solution in class (not the entire solution, but enough to get people working in the right direction). If you are not sure how to do a problem assigned to you, please come ask - but do it at least a day in advance, and not right before class.

Before doing assignment 0, you may wish to read my E11/E12 review, in particular 1st order step responses.

      1. pd Problem C,
      2. ke 1.35,
      3. rg 1.36,
      4. vk The ADC on the MSP430 has 10 bits. If the reference voltage is Vcc=3.3V, what is the resolution.
      5. The 3.3V power supply is usually not very accurate (+/-5% or so), so for more accurate conversions, the ADC10 has a 1.5 and 2.5V reference (see page 535 of the data sheet). Assuming the sensor is perfectly accurate, and the ADC10 reference voltage is set to 1.5V (and is also perfectly accurate), how accuarately can you measure tempearture in Celsius (see page 550 of the data sheet).
      6. mk Use the code below as the basis for a program that toggles the LED every time you hit the push button on the LaunchPad using interrupts on the push button input. Also add comments to the code.
      7. bk Why is the variable pbFlag declared to be volatile?
#include <msp430.h> 

#define LED BIT0
volatile int pbFlag=0;  // flag that gets raised to indicate interrupt.

void main(void) {
  WDTCTL = WDTPW + WDTHOLD; // Stop watchdog
  // Add your code to set up ports.

__bis_SR_register(GIE);  // enable interrupts.

  while (1){
     if (pbFlag) {
         pbFlag = 0;
         P1OUT ^= LED;  
     }
  }
}

// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void) {
  // Add your code to set pbFlag to 1 and clear interrupt flag
}
  • Asn 5:
      1. Problem D
      2. Problem E
      3. From text: 1.67
      4. 1.71
      5. 2.117a (STC=Single Time Constant, i.e., first order filter)
  • Asn 6:
    1. el, Show that the circuits in Figure 16.37 have identical transfer function and explain why the second circuit uses one fewer op-amps.
    2. tm, 16.19
    3. zm, 16.22
    4. nm, 16.30 (also plot the transfer function)
    5. gr, The circuit below is from MAKE magazine and is designed as a lie detector using galvanic skin response. Resistors marked 3M3 are 3.3 MΩ.
      • You should assume the baseline resistance of the skin is about 200 kΩ.
      • V+ = 5V (this is the positive supply).
      • V- = 0V (ground).
      • Assume the constant drop model for all diodes. D1-D3 drop = 0.6 Volts each, when on.
      • LED1 drop = 2.8 volts when on.

    Two electrodes labeled SKIN-1 and SKIN-2 are attached to two fingers and forms a voltage divider to ground (V-) through R4. If you experience stress, you sweat a little and the resistance between the electrodes decreases because of the increased conductivity at the skin-electrode interface. This is filtered (IC1A) and then amplified (IC2B). If the signal at the output of the amplifier is high enough, the LED turns on.
    a) What is the voltage at the non-inverting terminals of the op amps? Explain your reasoning.
    b) If the skin resistance has been constant for a long time, what is the baseline voltage at the output of IC1B? Explain your reasoning. Is the LED on or off?
    c) Find the transfer function between points A and B and verify the cutoff frequencies.
    d) Plot the overall frequency response (i.e., the Bode plot, just magnitude) between A and C.

    1. tx, The diagram below shows the results of the device in action as different questions are asked.
      a) From the circuit diagram explain why a drop in resistance increases the output voltage of the amplifier (Pin 7, IC1B).
      b) If the skin resistance starts at 200 kΩ and then drops suddenly, how low must the resistance go to light the LED (i.e., assume a step change in resistance)? State any assumptions.
      1. bz, Problem F
      2. ea, Problem G
      3. ka, Find the transfer function for a Butterworth low pass filter with the following characteristics
        • No more than 3dB of attenuation below 3kHz.
        • At least 50dB of attenuation above 8kHz.
      4. sca, Design a circuit to implement the filter above. Use the unity gain Sallen Key low pass filter with 10kΩ resistors

    1. For the 555 oscillator from Lab 1, determine the frequency of oscillation and the duty cycle if the potentiometer is at its midpoint and the "JSlow" jumper is not installed
    2. from text: 16.62, 17.18, 2.101, 2.102, 2.105, 2.117, 2.127

Labs

You should work on labs in groups of three or four, you will turn in one report per group.
Sign up for lab groups here.


Grading

Coursework Weight
Midterm exams #1, 2, 3
(Lowest exam counts 1/2 as much as others)
1/3
Homework
(Lowest homework will be dropped)

1/6
Labs
(Lowest lab counts 1/2 as much as others)
1/3
Project 1/6

Policy on working together

Homework: I encourage you to work together on homework, but don't blindly copy another students work.  You should fully understand all solutions to homework before submitting them.
Labs: I expect labs to be done as a group.  Each group will submit a single report (with all members of the group listed). 
Groups should work independently of one another - you may discuss particular issues, but do not share data or reports.
Projects: Projects may be either individual, or as a group. 
Exams: Exams are to be solely your own work.  The format of exams may vary, but it is never permissible to seek help from another individual.

Statement on Accommodations

"If you believe you need accommodations for a disability or a chronic medical condition, please contact Student Disability Services (Parrish 113W, 123W) via e-mail at studentdisabilityservices@swarthmore.edu to arrange an appointment to discuss your needs. As appropriate, the Office will issue students with documented disabilities or medical conditions a formal Accommodations Letter. Since accommodations require early planning and are not retroactive, please contact Student Disability Services as soon as possible. For details about the accommodations process, visit the Student Disability Services website. You are also welcome to contact me [the faculty member] privately to discuss your academic needs. However, all disability-related accommodations must be arranged, in advance, through Student Disability Services."