Low-Pass and High-Pass Filters

In this experiment, we are catching a glimpse of two very simple designs of filters. The first one is a low-pass and the second one is a high-pass filter. A low-pass filter is a filter the lets the lower range of frequencies to pass and blocks the upper end of the frequency range. On the other hand, a hight-pass filter lets the upper range of frequencies to pass and stops the lower range.

Both of these filters are consisted of only two components: a resistor and a capacitor. First you are to assemble the low-pass filter on a breadboard as shown in the following figure (Figure 1):

 

Low-Pass Filter
Figure 1 - Low-Pass Filter

XFG1 is the function generator and XSC1 is the oscilloscope. The signal would be a sine wave with 5Vpp and 0V offset. You are to use a table and set the frequency of the function generator to the following values and write down the output voltage that oscilloscope is showing:

 

Frequency (Hz) LP Magnitude (V) HP Magnitude (V)
20    
30    
40    
50    
60    
70    
80    
90    
100    
200    
300    
400    
500    
1000    
2000    
3000    
4000    
5000    
10000    
11000    
12000    
13000    
14000    
15000    
20000    

Table 1 - Data

Once you have gathered the data, open up an Excel sheet and enter the frequencies and the voltages in columns. The next step is to assemble the high-pass filter on the breadboard according to Figure 2:

 

High-Pass Filter
Figure 2 - High-Pass Filter

Use the same range of frequencies and write down the voltages in the appropriate cells in your Excel sheet. The last part of the lab is to create a graph from your data in Excel showing both filters at once. I will go over how to do that during class.