CMOS and TTL Transfer Characteristic Curves

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

Parts List

Equipment

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 the "Lab Resource” web page for links to a representative sample of manufacturers (for data sheets) and distributors (for price and availability information). You may 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 and sometimes the datasheets.] 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) V_OHmin
   (g) V_OLmax
   (h) V_IHmin
   (i) V_ILmax
   (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.
    

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 V_OH and V_OL. Compare your measured results with the manufacturer’s data sheet minimum and maximum values to determine whether or not your device meets specifications. [Hint1: A table would be appropriate here]. [Hint2: Recall that “compare” is lab handout code for “calculate percentage error and discuss your findings.”]
    
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. Discuss differences in your lab notebook.
     

All done!