Special Circuit

Required of all software dominant projects

For those registered in ECE445 (old ECE345), who are completing the special circuit to fulfill the hardware requirement:
You are required to include the special circuit in your proposal, design review, and final paper. You must also demo your circuit during the formal demo week, or before at the convenience of your TA and the professor. At that demo, you must present a schematic of your circuit, the tolerance analysis, and appropriate supporting measurements.

For those NOT registered in ECE445, but who must complete the special circuit:
You will be assigned a TA, a locker, and a special circuit which generally takes about 12-15 hours to complete. When you have it designed and built, you will give a functional demonstration to your TA, who will then inform the professor who will inform undergraduate advising that your task is complete. You are NOT required to attend any of the classes, reviews, demos, or presentations. You are also NOT required to write a proposal or final paper. Sign up as a Special Circuit student under the "Lab Access" section on the projects page.

Click here to jump to the Fall 2005 Circuit

Circuit #1

Design, assemble, and test, a clock (timer) circuit with the following characteristics. The design characteristics are below, with the (±) values the acceptable tolerances of the tested circuit (and consequently, drive the circuit component value tolerances).

• The clock should be 0-5 v (± 5 %).
• Your frequency should be selected from the table below (± 3%), with a pulse width (± 5 %).
• Your pulse width may be either 1, 10, or 100 micro secs, but the selected width you choose must be such that the duty cycle of the clock is < 50% high.
• Using a linear 555 timer component is acceptable.

Some typical frequencies that may be assigned include: 2 Hz, 600 Hz, 3700 Hz, 11000 Hz.

Your two specification tests can be defined for the specification limits of frequency and/or pulse width in the design. An example of one of the specification tests could be: Given your frequency chosen is 900 Hz, the (± 3%) allows the tolerance in the output to be 873-927 Hz. Find the values for the frequency setting resistor value (measured) for the minimum and maximum frequency (measured). Document the results.

Circuit #2

Design, assemble, and test, a small-signal low-frequency (< 100 kHz) amplifier circuit with the following specifications (tolerances):

• Frequency response: Lowpass or Highpass, to be assigned
• Rolloff: Single pole response is sufficient
• Gain in passband: To be assigned; (± 5%)
• Corner frequencies: To be assigned; (± 3%)
• Input impedance: 500 ohms at 1 kHz; (± 5%)

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a bias resistor and see how it affects the passband gain. What range of values are acceptable for that resistor? Document the results.

Circuit #3

Design a voltage regulator that meets the following specifications:

• Output voltage level within 3% of assigned value (TA will give you the voltage level)
• Must be able to deliver a maximum current of 2A
• Must be robust to reverse polarity of the input supply voltage

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values are acceptable for that resistor? Document the results.

Circuit #4

Design an audio oscillator that meets the following specifications:

• Four different frequencies (TA will give you the voltage level)
• THD less than 1% for frequencies above 1 kHz and less than 3% for those around 100 Hz
• Output voltage level should be individually adjustable for each frequency
• Sequencing rate control between 3 seconds and 30 seconds (TA will give the value)

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance.

Circuit #5

Design and implement a simple ultrasonic transmitter/receiver meeting the following specifications:

• Power supply should be 9V, 12V or 15V (TA will assign the voltage level)
• The transmitter should generate a signal between 40-60 kHz. (TA will assign center frequency)
• The receiver stage should receive the center frequency generated by the transmitter and should trigger an electronic device (given by the TA)

For the tolerance analysis portion of your senior project, you must choose two of the above components that affect the performance of your circuit. Document your results.

Circuit #6

Design, assemble, and test an audio amplifier with the following characteristics:

• The amplifier must operate within the audio frequency range (exact values determined by TA)
• The output decibel in the passband must be within +/- 5% of a value to be determined by your TA
• The output impedance must be 4 or 8 ohms (assigned by TA)

As part of the tolerance analysis, you must select two components of your design and determine their effect on the output of the system. Analyze the appropriate ranges of values for given components and document the results.

Circuit #7

Design, build and test a current driven square wave generator with the following specifications:

• A minimum pulse height in the range of 3-5V, to be assigned by your TA
• A minimum pulse width in the range of 1-10s, to be assigned by your TA
• The output pulse frequency must be dependent upon the current input from a photodiode
  • Correlation between input current and output frequency is your choice
  • Must have accurate current measurement within ± 3%

As part of the tolerance analysis, you must select two components of your design and determine their effect on the output of the system. Analyze the appropriate ranges of values for given components and document the results.

Circuit #8

Design build and test a circuit to modify the speaker output signals from a computer.

You will be provided with the left and right speaker signals separately.

The circuit should have the following specifications:

• Create a subwoofer output that utilizes the lowest 100-300Hz, to be assigned by your TA
• Modifies the left and right speaker inputs separately in one of the following frequency windows -12dB to +12dB
• The unchanged frequency bands must remain within 3% or their original values. (spectral density)
• The output impedance must be 4-5 Ohms

As part of the tolerance analysis, choose two components of your design and determine their effect on the output of the system.

Circuit #9

Special circuit, Fall 2004

Design, build and test two notch filters, one passive and one active.

• Each filter should block f=60 Hz.
• Measure the -3 dB points and calculate the bandwidth of each filter.
• Calculate the quality factor, Q, of each filter.

As part of the analysis, choose two components of your design and determine their effect on the output of the system. Additionally, explain the performance differences between the passive and active filters, specifically explain how changes in the source and load effect each filter.

Circuit #10

Special circuit, Spring 2005

Design, assemble, and test a narrowband bandpass filter with the following tolerances:

• Center frequency: To be assigned in 1-10 MHz band (± 3%)
• 3-db bandwidth: Must be 0.01 percent of center frequency, ex. if fc = 5 MHz, the BW = 500 Hz.
• Filter should be constructed using an active topology using as few components as possible (BiQuad, Sallen-Key for example)
• Rolloff > -200 dB/decade
• We may also add a specific time response requirement as well

Simulate your design in PSpice, ADS, etc. As part of the tolerance analysis, choose two components of your design and discuss their effect on the output of the system.

Circuit #11

Special circuit, Fall 2005

Design, assemble, and test a linear DC voltage regulator with the following specs:

• 3% output voltage regulation (assigned 5V, 12V, or 15V dc)
• input voltage range of 1x to 2x assigned output voltage (i.e. for 10V output, input voltage is 10-20V)
• Must be capable of .5A output current
• >70dB noise rejection at 10kHz

For the tolerance analysis portion of your senior project, you must characterize your circuit for two (2) of the above specifications. For each spec, you must choose a component that affects your circuit's ability to stay within the given tolerance. For example, you could pick a resistor and document what affect is has on the output voltage level. What range of values are acceptable for that resistor? Document the results.