Lab #11: ADC to DAC SAIT- ENT-DIGI-260

Lab #11: ADC to DAC

CreatedApril 2008

Objectives:

  1. Build an ADC to DAC circuit.
  2. Analyze the operation of anADC to DAC circuit.
  3. Record observations of a functional ADC to DAC circuit.

Pre-Lab Preparation:

  1. Attend lectures and review the theory of operation of ADCs, DACs and related circuits.

Equipment Required:

  1. Experimenter’s board with 5V power supply
  2. Function Generator
  3. Oscilloscope
  4. Dual Power Supply
  5. PC with access to specification sheets
  6. Parts kit
  7. Misc parts supplied in lab

Additional Notes:

  1. Marks will be instantly deducted from your lab if you fail to set the function generator or supply voltages properly.
  2. This lab combines the previous ADC and the DAC labs. Please reference these labs for information on how to configure the devices.
  3. Wiring neatness is important for this lab. All components must be kept low to the board.(trim leads if necessary).
  4. You are not permitted to exchange EWB files! Create your own EWB files. A mark of 0 will be assessed for labs that contain plagiarized elements.

Procedure 1:

Built, analyze and comment on the operation of an ADCusing Electronics Simulation software.

1.Using Electronics Simulation software, design a functional 8-bit Analog to Digital converter to an 8-bit Digital to analog converter circuit.

  1. Use the model for the ADC and the V-DAC.
  2. Use 5 Volts (Vcc) as supply voltages and ground as the references.
  3. Connect an oscilloscope to the signal input to the ADC and to the signal output from the DAC.
  4. Connect a bar LED configuration to the output of the ADC (no resistors are required for this device in EWB).
  5. For the ADC, connect the EOC to the SOC. Connect a switch to temporarily short the SOC to ground (simulation may not function otherwise). Connect the OE to the appropriate logic value for the device to provide a continuous output.
  6. Connect a function generator at the input of the ADC. Determine the input voltages required.

2.Apply a 10 kHz sine wave to the input.

3.Answer the questions in the worksheet toward the end of the lab.

4.Disconnect the lower 4 bits. Observe the output and answer the questions in the worksheet.

5.Demonstrate the circuit to the instructor.

6.Ensure the diagram is labeled and all the traces are routed neatly. Print the labeled diagram and include it with your lab submission.

7.Proceed to procedure 2.

Procedure 2:

Design,build and verify the output of an ADC to DAC circuit using ICs.

1.Refer to previous labs for specific configuration information for ADC and DAC ICs.

2.Configure an ADC to DAC using ICs from previous labs. Refer to diagram #1 for general configuration information. For the ADC clocking use a 10kΩ resistor and a 470ρF capacitor. Use 4.7kΩ resistors and 0.1 µF capacitors for all other values.

3.Add an op amp to the output. Utilize +12/-12 as applied voltage values.

4.Apply a 0-5V sine wave, 30Hz to the ADC input and observe the condition of the input and output. Both the input wave and the output wave should have the same amplitude, offset and phase.

5.Demonstrate the circuit to the instructor.

Diagram #1: ADC-DAC-AMP Configuration, Procedure 2

Procedure 3:

Analyze various functions and limitations of an ADC to DAC circuit using ICs.

1.Use the circuit from procedure 2.

2.Apply a 1.5kHz sine wave to the input and record your observations in the worksheet.

3.Change the value of the clocking resistor from 10kΩ to 1kΩ and repeat step 2. Record these new observations in the worksheet and answer the questions.

4.Connect a wire to the Clock In and short it to ground. Do this several times while the device is active. Record the observations in the worksheet.

WORKSHEET

Measurements and observations for procedure #1 (simulated ADC-DAC)

  1. What is the period of the EOC output of the ADC? What does this time represent?
  1. What happens when the input voltage is not set correctly? Explain.
  1. Define SOC and EOC, and explain their function.

Measurements and observations for procedure 2:

  1. Does the output frequency and voltage match the input frequency and voltage?

If yes, demonstrate to the instructor and proceed to the next lab (if not, make the necessary circuit adjustments).

Measurements and observations for procedure 3:

1.What happens to the output when a 1.5kHz sine wave is applied to the input? Explain the type of error you get and why this is a problem.

2.What is the function of the R and C at the CLK input pins?

3.What happens to the output with a decrease of the resistor value? Explain why you get these results.

4.What happens to the output when you short the clocking input? Explain.

Signatures:

Procedure 1 Circuit: ______

Procedure 2 Circuit demonstration: ______

Procedure 3 Circuit Demonstration: ______

Submit:

Worksheets

Labeled diagram from procedure 1

Student Name: ______Date: ______

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