EGR 240 Lab 3. September 21 - 26, 2006.

EXPERIMENT: D/A Converter – PSpice and Soldering

References

  1. Lecture slides D2.2: Digital to Analog (D/A) Converter and D3.2: Analog to Digital (A/D) Converter.
  2. Kerns and Irwin textbook: Section 8-6, 8.6.1 on pages 311 – 314.
  3. PSpice Tutorial (.pdf file available on class website).

LAB

Part A. PSpice.

Simulate the 2R-R resistor network shown in Fig. 1 using PSpice by following the PSpice Tutorial that you can download from the class website. Print out your PSPice circuit diagram and the simulated waveform.

Figure 1

Have your lab instructor sign your results.

Part B. Soldering.

Solder the circuit shown in Figure 2 on your circuit board.

Figure 2

Have your lab instructor check your results.

Part C. Circuit Test.

1.Connect the output, gt, of your D/A converter to the left-most red LED on the PLDT-3 board. Connect B3, B2, B1, and B0 to the four right-most toggle switches on the PLDT-3 board. Connect Vin to a variable power supply (0 – 5V) with the voltage set initially to zero.

2.Turn all toggle switches off. Set Vin to some voltage between 0 and 5 volts. Measure this voltage with the multimeter and record the voltage, Vin, in Table 1. While maintaining this voltage, turn on the toggle switch B3. If the green LED is lit, leave it on; otherwise, turn it off. Repeat this procedure for B2, B1, and B0. The resulting switch setting will be the 4-bit binary number representing the analog voltage, Vin.

3.Measure five different voltages using this method and record your results in Table 1.

Table 1

Analog voltage, Vin / 4-bit Binary value / Hex value
0 V
5.0 V

Have your lab instructor sign your results.

Answer questions 9 – 12 on the class website for next lab:

9. List the steps that you followed in simulating the circuit in Figure 1 using PSpice and describe how you can install a version of PSpice on your own computer.

10. Derive the equation for V in Fig. 1 in terms of B3, B2, B1, and B0.

11.Explain why the procedure you followed in Part C gives a hex value proportional to the voltage applied at Vin.

12. Explain how the procedure you followed in Part C implements the successive approximation method of implementing an A/D converter.

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