Lab 9

LAB 9-CMOS and TTL Transfer Characteristic Curves

Introduction

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

Objectives

	Practice finding technical information from manufacturer’s data sheets.
	Extract needed technical data from a data sheet.
	Measure transfer characteristics for typical digital logic families.
	Compare measurements with manufacturer’s specifications.

Parts List

	SN74HC00N -- CMOS quad NAND gate
	SN74S00N (or SN7400N or SN74LS00N)-- TTL quad NAND gate
	MM74HC14N -- CMOS hex inverter with Schmitt trigger inputs

Equipment

	Agilent 5000 MSO
	Agilent 33120A Function/Arbitrary Waveform Generator
	Fixed 5V power supply
	Breadboard

Prelab

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). You may also try some of the semiconductor-oriented search tools such as ChipCenter.

1.Find 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.]

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) V_OHmin
    (e) V_OLmax
    (f) V_IHmin
    (g) V_ILmax
    (h) nominal supply voltage
    (i) 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. Plot the expected output voltage as the input voltage varies continuously from 0V to 5V.

Lab

1. Mount the SN74HC00N on your breadboard. Supply power to the chip from the fixed 5V d.c. source. Check the data sheets for the correct pins for the power supply (labeled Vcc and Gnd).

2.Select one of the four NAND gates for your tests, and tie its inputs together. Connect all unused inputs to ground.

3.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).

4.Make sure that your function generator, oscilloscope, and 5V fixed power supply all have a common ground connection.

5. 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. Change the function generator frequency to 0.1 Hz (that is, one tenth of one hertz) before continuing.

6.Now, adjust the oscilloscope for “X-Y” operation: Press “Horizontal" button, then select "Time Mode" , then "XY" option”. 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.

7. Press “Waveform -> Display” and select “Infinite Persist”. Can you explain what you see on the screen?

8.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.

9.Record a screenshot of the transfer characteristic curve to your lab book.

10.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. [Hint: A table would be appropriate here to compare datasheet values with your values].

11.Repeat Steps 1 to 10 using the SN74S00N.

12.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.

13.Repeat Steps 1 to 9 using the MM74HC14N.

14. 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. Calculate the actual hysteresis. Discuss differences in your lab notebook.

All done!

	Clean up your work area
	Remember to submit your lab notebook for grading at the beginning of next week's lab.
	Include prints of the oscilloscope with all your measurements, results, conclusions, etc.