EET230_Lab5_Taylor_Jason

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ECPI University, Virginia Beach *

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230

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Electrical Engineering

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Apr 3, 2024

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Digital to Analog Conversion (DAC)/Analog to Digital Conversion (ADC) Objectives  Study and implement of Signal Conversions  Explain how DACs operate  Explain how ADCs operate  Multisim Simulation Analysis of signal conversions  Explain the basic concepts of a digital signal processor (DSP) Procedure Construct and use multisim to simulate analysis for the following ADC/DAC circuits and explain their operation by completing truth table for inputs/outputs. For each circuit, provide a couple screenshots , a ll screenshots must capture date of the simulation. Digital to Analog Convertors Multisim Simulation 1) Binary Weighted Digital to Analog Converter Figure 1 shown below is a binary-weighted Digital-to-Analog converter. Build the circuit in multisim and answer the following questions in your simulation a) Close each switch individually to determine how many volts each switch contributes to Vout. List those four values in a data table. S1 S2 S3 S4 -8.003 -4.003 -2.003 -1.003 b) The current through If is always equal to Isum (T or F)? F c) Which switches need to be closed to yield the following outputs: -8V, -4V, -6V, -11V? S1=-8V , S2=-4V, S2 & S3=-6V, S1, S2 and S4 all closed= -11V d) How many different digital numbers can be represented with the four input switches ? 32 Different combinations. e) To make a 5-bit D-to-A you would need to add another switch and resistor to the left of D3. What size would the resistor be? 6.25KΩ4 Lab Assignment 5

Figure 1 2) Virtual DAC The DAC shown in figure 2 outputs a voltage proportional to it's 8-bit binary input. The + Vref input is set to 5V. This in turn sets the maximum output at 5V. Since there are 256 possible binary input

steps then the volts per step will be 5V / 256 = 19.53mV. The word generator is used to count from 0 to F repeatedly (the 4 high-order inputs are not used in this case). a) On a piece of paper, sketch and label the analog output value. ("Expand" the scope and take accurate measurements for each step voltage and time per step.) b) Change the "Final" address in the Word Generator to FF so that all 256 steps will be output. Sketch and label the resultant waveform. (The scope Time base and V/Div will need to be changed to see the entire waveform.) 5V Vref VCC T R X X X X 0 0 0 0 15 0 16 31 XWG1 A B T G XSC1 Analog Output U1 VDAC + - D0 D1 D2 D3 D4 D5 D6 D7 VDAC

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Figure 2 3) R2R Ladder Digital to analog converter The circuit shown in figure 3 below is an R2R ladder. Observe the output for different input combinations. Carry out the calculation and check your calculated and simulated results 1s Key = A 2s Key = B 4s Key = C 8s Key = D V1 3.2 V R1 20kΩ R2 20kΩ R3 20kΩ R4 20kΩ R5 20kΩ R6 10kΩ R7 10kΩ R8 10kΩ R9 10kΩ 1 2 3 U1 OPAMP_3T_VIRTUAL 0.200 V + - Binary Input Analog Output R-2R resistor network Scaling Amplifier

Figure 3 Individual Switch Values S1 -0.75V S2 -1.5V S3 -3V S4 -6V Switches add there values together when switched. All switches together will equal -11.25V. 4) Analog to Digital Converter Figure 4 below is used to convert the Analog Vin into a binary number at the output of the ADC. This binary output is displayed in hex on the two seven-segment displays. The Analog Vin is varied by changing the potentiometer setting (a and Shift-a). a) Create a data table of Analog Vin versus hex output for eleven steps in Vin from 0V to 5V in 0.5V increments. 5V FF 255 4.5V E6 230 4V CC 204 3.5V B3 179

3V 99 153 2.5V 7F 127 2V 66 146 1.5V 4C 76 1V 33 51 .5V 19 25 b) Convert all of your HEX answers to decimal. Do they appear to be taking approximately equal steps? It seems to be a close step down .

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Figure 4 Submission: Save your Multisim simulation file as EET230_Lab5_YourName. All screenshots of Multisim must capture date of the simulation. Follow the submission instructions in Canvas to upload your lab file.