1 Frequency Response of Networks ECE 300 Lab 1 Frequency Response of Networks In this lab we will calculate and measure the frequency response of the passive networks shown below Circuit 1 Circuit 2 R1 Vo C1 10n 10n Vin Vin 3900 C1 3900 R1 Vo We will analyze this circuit three ways and compare all results First we will find the magnitude of the transfer Vo j by hand and then calculate the value of the function for several frequencies Next we will Vin function simulate the response of the circuit using PSpice with an AC sweep Lastly we will measure the response of the circuit in the lab at several different frequencies All this data will be entered into an Excel spreadsheet and plotted 1 A Pre Lab Calculations The steps listed below must be completed for each circuit before you come to lab 1 Calculate the transfer function Vo j Vin Vo 2 Calculate the magnitude of the transfer function Vin j 3 Evaluate the magnitude function from item 2 above for frequencies from 1 Hz to 100 kHz 4 Simulate the circuit with PSpice using an AC analysis You will need to use the part called VAC and set up an AC sweep from 1 Hz to 100 kHz Make sure that you specify a logarithmic sweep in decades An example circuit and setup is shown below Vin R1 AC Sweep 3900 V1 Magnitude 1 Phase 0 Vo C1 10n 0 1 5 Export the PSpice data to Excel and arrange the spreadsheet so that you can plot the calculated data from item 3 the PSpice data and measured data on the same plot 1 B Laboratory Procedure 1 Wire circuit 1 Use a frequency generator as the input and use an oscilloscope to measure the waveforms The diagram below may or may not help you XSC1 XFG1 G A B T R1 C1 10nF 3 9kohm 2 With channel A measure Vin With channel B measure Vo For each gain measurement measure both the input and output waveforms because the amplitude of the signal generator s output may change with frequency 3 Measure Vin and vo for several frequencies and fill in Table Frequency Response of Networks 1 You should make a number of measurements near 4 kHz Why Vo 4 Using Excel generate a plot of Vin j versus frequency with the measured data PSpice data and calculated data Plot all three curves on the same graph Repeat the above procedure for Circuit 2 and record the measured data in Table Frequency Response of Networks 2 2 Table Frequency Response of Networks 1 Measured data for Circuit 1 vo Vin Frequency v r Gain o Hz s vs Gain in Decibels v 20 Log10 o vs 3 4 Table Frequency Response of Networks 2 Measured data for Circuit 2 vo Vin Frequency v r Gain o Hz s vs Gain in Decibels v 20 Log10 o vs 5 6
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