Interfacing a Transducer to an Analog-to-Digital Converter and Interfacing Digital-to-Analog Converters to Loads

Interfacing a Transducer to an Analog-to-Digital Converter and Interfacing Digital-to-Analog Converters to Loads

  1. Watch video Week 5 – Op Amp DAC Circuit (Right click, save as)
  2. Design an 8-Bit DAC Circuit – Calculate the values for all resistors
  3. Include calculations and schematic in a Word document entitled: “HW5_StudentID”, with your student id substituted in the file name.  Show all work for full credit.
  4. Upload file “HW5_StudentID”

Complete circuit in multisim!

 

Lab

Interfacing a Transducer to an Analog-to-Digital Converter and Interfacing Digital-to-Analog Converters to Loads

The purpose of this lab is to allow students to gain experience constructing Digital to Analog Converters in Multisim. Students will extend the concepts learned in the module and homework to build an 8-Bit DAC. Several binary inputs and the associated analog output values measured with a virtual digital multimeter will be captured in screenshots.

  1. Watch the video Week 5 – Op Amp DAC Circuit
  2. Determine the values of all the remaining seven resistors and fill in the table 1.

Table1:

Resistors Values
R1 1k Ω
R2
R3
R4
R5
R6
R7
R8
  1. Recall the binary to decimal conversion and fill the table below:
Bits Binary Input Decimal conversion
MSB(S1) 1000 0000
S2
S3
S4
S5
S6
S7
LSB(S8) 0000 0001
  1. Construct an 8-bit binary weighted DAC in Multisim and measure the output voltage Vout using the multimeter and record the computed gain below.

Table2:

Bits Binary Input Vin Rn(n = 1,2,3,4,5,6,7,8) RF Output Voltage (Vout) Voltage Gain (Av)
MSB(S1) 1000 0000
S2
S3
S4
S5
S6
S7
LSB(S8) 0000 0001
  1. Take the screenshots of Vout measurements for the input/output combination for each of the above 8-bits.
  2. Answer the following questions:
    1. Determine the approximate value of RF which results in accurate digital to analog conversion.
    2. Write the expression for Vout in terms of Vin, RF and R for each bit. Also, express Vout in terms of all 8 input voltages.
    3. Starting from the least significant bit to the most significant bit, what is the effect of feedback resistance on the output voltage?
    4. From your measurements, does increase in the digital value result in increase in analog value? Please explain.
    5. Is the voltage gain of the op Amp different for each bit? Please explain why?
  3. Create a new word document called “Lab5_StudentID.docx” with your GID substituted into the file name.
  4. Verify all calculations from analysis and measurements from simulations. Save the results along with the table and paste the screen captures in the word document. Make sure to answer the questions.
  5. Upload file “Lab5_StudentID” in Blackboard
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