Lab Assignment 5 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. For each circuit, provide a couple screenshots, all screenshots must capture the 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. b) The current through If is always equal to Isum (T or F)? c) Which switches need to be closed to yield the following outputs: -8V, -4V, -6V, -11V? d) How many different digital numbers can be represented with the four input switches? 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? Digital Input Key= D3 Key = D2 Key-95 R1 Key -S1 .020u D1 DO V1 20kQ R 5V 12.5kQ 25kQ 50kQ R2100kQ FO R6 0.020u Figure 1 R3 Analog Vout OPAMP_ST_VIRTUAL 10kQ -0.400m ARI 2) Virtual DAC The DAC shown in figure 2 outputs a voltage proportional to its 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) by doing the following steps: ➤ Single-click on the Word Generator icon in the far-right column of icons in the Multisim screen to put it in your workspace (XWG) and move it to where you want it ➤ Double-click on the Word Generator icon in your workspace ➤ In the pop-up window, click on Set ➤ In Preset Patterns, click on the Up counter button ➤ Type 0010 in the Buffer Size box ➤ Close the pop-up window ➤ To get XSC1 in your workspace, single-click on the Oscilloscope icon in the far-right column of icons ➤ To place the VDAC icon in your workspace, click on Place in the top menu bar, select Component, then type VDAC into the Component entry box a) Play with the oscilloscope's Timebase Scale and Channel A Scale until you get a reasonably- sized image of the full output. Take a screenshot. b) Change the Buffer Size in the Word Generator to 0100 so that all 256 steps will be output. Adjust the oscilloscope's Scales and take a screenshot. XWG1 ooo ooo ooo oo000000 O oooooooo oo000000 31 T VCC 5V Vref DO D1 D2 D3 D4 D5 D6 D7 U1 + VDAC VDAC XSC1 Analog Output 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 Binary Input 1s R1 W 20ΚΩ Key = A V1 2s R2 3.2 V 0 20kQ Key = B R5 W 20ΚΩ R7 10kQ R8 10ΚΩ 4s R3 W 20ΚΩ R9 10ΚΩ Key = C 8s R4 ° ww 20ΚΩ Key = D R-2R resistor network Figure 3 1 2 R6 www 10ΚΩ U1 OPAMP_3T_VIRTUAL Analog Output Scaling Amplifier 0.200 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. b) Convert all of your HEX answers to decimal. Do they appear to be taking approximately equal steps? 5V 1000 Key-A 50% Analog Vin U3 DCD_HEX U4DCD_HEX Hex Output U1 0.000 5V VCC VIN VREFP VREFN Soc Start pulses OE 8888888 DO D1 D2 D3 Digital Output D4 D5 D7 EOC + വ 10KHZ 5V A DC Submission: • • • • Figure 4 Save your Multisim simulation file as EET230_Lab#_YourName. Be sure Submit word document file (no zip file) All screenshots of Multisim must capture the date of the simulation. Attach each circuit file of your experiment's simulation separately.