Operational Amplifier Applications Unit 3 – Low Pass Filter
Exercise 1 – Low Pass Filter Frequency Response
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the frequency
characteristics of an active low pass filter by using an oscilloscope to analyze input and output
waveforms.
EXERCISE DISCUSSION
- Active low pass filters can be designed for different types of frequency response. Circuit
component relationships define the type of frequency response. - Chebyshev, Butterworth, and Bessel are three common types of active low pass filters.
- The Chebyshev filter has stopband characteristics that are close to those of an ideal low pass
filter. - Butterworth filters exhibit passband characteristics that are close to those of an ideal filter.
- Plot filter response curves on semilogarithmic graph paper to clearly illustrate rolloff
characteristics of the filter. Output voltage (or dB gain) is assigned to the vertical (y) axis.
The horizontal (x) axis is scaled logarithmically. - A frequency decade is defined as a factor of 10, i.e.: 100, 1k, 10k.