Lab 9

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CMOS and TTL Transfer Characteristic Curves

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Introduction

In this lab you will learn how to measure the transfer characteristic of a digital inverter (a 2-input NAND with inputs tied together). You will measure the characteristics of standard CMOS and TTL logic families, as well as a device that exhibits hysteresis, specifically, and inverter that has a Schmitt trigger input.

Objectives

bulletPractice finding technical information from manufacturer’s data sheets, and pricing information from parts distributors
bulletExtract needed technical data from a data sheet
bulletMeasure transfer characteristics for typical digital logic families
bulletCompare measurements with manufacturer’s specifications

Parts List

bulletSN74HC00N -- CMOS quad NAND gate
bulletSN74S00N -- TTL quad NAND gate
bulletMM74HC14N -- CMOS hex inverter with Schmitt trigger inputs

Equipment

bulletAgilent 54622D MSO
bulletAgilent 33120A Function/Arb Generator
bulletFixed 5V power supply
bulletBreadboard

 

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Prelab

  1. Semiconductor manufacturers now publish most of their data sheets on their websites. Data books are still available, but you will often find that a web-oriented parts search is much quicker. See my “Resources” web page (www.rose-hulman.edu/~doering/homepage/resources.htm) for links to a representative sample of manufacturers (for data sheets) and distributors (for price and availability information). Also try some of the semiconductor-oriented search tools such as ChipCenter.

    Retrieve the data sheets for the three parts indicated in the “Parts List” section above. [Hint: Sometimes searching for a known part number at the distributor will reveal the specific manufacturer.] Record the details of your search method!
     
  2. Create a table that identifies the following information for the SN74HC00N and SN74S00N devices:
    (a) manufacturer
    (b) device type (what is the device?)
    (c) package type (is it a DIP, SOIC, TSOP, etc.?)
    (d) cost in single quantity
    (e) cost in quantity of 100 (look for volume discount... multiplying your result from part (d) by 100 isn’t correct)
    (f) VOHmin
    (g) VOLmax
    (h) VIHmin
    (i) VILmax
    (j) nominal supply voltage
    (k) minimum supply voltage
    (l) maximum supply voltage
    (m) minimum operating temperature
    (n) maximum operating temperature.
     
  3. Draw the ideal voltage input-output transfer characteristic curve of a two-input NAND gate that has both input terminals tied together. That is, plot the expected output voltage as the input voltage varies continuously from 0V to 5V. Use a supply voltage of 5V.
     
  4. A photocopy of your prelab pages is due at the beginning of the class the day before lab. For this lab also attach the first page of each of your three data sheets.
     

Lab

Please use the Lab Help Queue to request assistance in lab.

  1. Mount the SN74HC00N on your breadboard. Insert wires so as to power the chip from the fixed 5V source. Select one of the four NAND gates for your tests, and tie its inputs together. Connect all unused inputs to ground.
     
  2. Set up your function generator to produce a triangle waveform that swings between 0 and 5V at a frequency of 1 kHz. Hint: You will need to adjust the offset.
     
  3. Make sure that your function generator, oscilloscope, and 5V fixed power supply all have a common ground connection.
     
  4. Apply the function generator signal to the remaining input terminal of your NAND gate. Observe the input signal on oscilloscope Channel 1, and observe the output signal on Channel 2. Make sure that the oscilloscope waveform makes sense. Change the function generator frequency to 0.1 Hz (that is, one tenth of one hertz) before continuing.
     
  5. Now, adjust the oscilloscope for “X-Y” operation: Press “Horizontal -> Main/Delayed” button (look for the zone called “Horizontal”, then press the button), then select “Softkey -> XY”. Quick tip: Press and hold any button on the oscilloscope to see a context-sensitive help screen.  Set both channels to 1 volt per division. Adjust the vertical and horizontal positions to place the origin at the bottom left of the screen. At this point you should see a single moving spot tracing out the input/output curve.
     
  6. Press “Waveform -> Display” and select “Softkey -> Infinite Persist”. Can you explain what you see happening on the screen?
     
  7. Now try increasing the function generator frequency to 1Hz, then to 10 Hz, and then to 1kHz. Make sure that you have a complete curve with no gaps.
     
  8. Record a screenshot of the transfer characteristic curve to your lab book.
     
  9. From your measured plot, determine the actual values of VOH and VOL. Compare your measured results with the manufacturer’s data sheet minimum and maximum values to determine whether or not your device meets specifications. [Hint: A table would be appropriate here].
     
  10. Repeat Steps 1 to 9 using the SN74S00N.
     
  11. Compare the transfer characteristic curves for your two devices. Discuss the similarities and differences between the two devices. Also compare your results with the ideal transfer characteristic.
     
  12. Repeat Steps 1 to 8 using the MM74HC14N.
     
  13. From your measured plot, determine the actual values of the low-to-high and the high-to-low threshold voltages. Compare to the manufacturer's data sheet.
     

All done!

bulletClean up your work area
bulletRemember to submit your lab notebook for grading at the beginning of next week's lab

 

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 ECE333: Digital Systems (W 2002-03)
Department of Electrical and Computer Engineering
Rose-Hulman Institute of Technology


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Last updated: 03/10/05.