Operational Amplifier Applications Unit 5 – Band Pass Filter
Exercise 2 – Band Pass Filter Phase Response
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the phase response of an
op amp band pass filter circuit. You will verify you results with an oscilloscope.
DISCUSSION
- The phase response of a bandpass filter is a combines the phase responses of the low pass
and high pass filters. - Phase shift is about − 45 ° at the corner frequency of the high pass filter or at the lower cutoff
frequency of the bandpass filter. Phase shift increases toward − 90 ° as frequency decreases. - Phase shift is about +45° at the corner frequency of the low pass filter or at the upper cutoff
frequency of the bandpass filter. Phase shift increases toward +90° as frequency increases. - At the center frequency the bandpass filter has a net phase shift of about 0°.
- The bandpass filter used in this unit has a phase shift caused by the inverting op amp. The
additional phase shift is − 180 ° and is created by the reactive components in the op amp
feedback and input circuit. - The overall phase shift of the bandpass filter circuit is a combination of the op amp inversion
and the individual capacitor phase shifts.