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):
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:
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.