ECE 3074
Experiment:Active Filters
Name:______
Date:______
Analysis
Bandpass Filters
The component values for the bandpass filter circuit are:
fo = 800 Hz / Value / fo = 2.4 kHz / ValueC / 47nF / C / 47nF
R1 / R1
R2 / R2
R3 / R3
The Bode plots for the bandpass filters when VS = 1V:
Fourier Components of a Square Wave
The first three Fourier componentsfor a square wave with a frequency of 800 Hz and an amplitude of 2V peak-to-peak are:
Component / Frequency (Hz) / Amplitude (V)n = 1
n = 2
n = 3
The expected magnitude and phase shift of the first three Fourier components at the output of the active filter:
Active Filter withfo = 800 Hz / Active Filter with
fo = 2.4 kHz
Magnitude (V) / Phase Shift (degrees) / Magnitude (V) / Phase Shift (degrees)
n = 1 / n = 1
n = 2 / n = 2
n = 3 / n = 3
The equation that describes the output voltage for the active filter with fo = 800 Hz is
Vo= ______
The equation that describes the output voltage for the active filter with fo = 2.4kHz is
Vo= ______
Modeling
The frequency response of the bandpass filters (VS = 1V)is shown below.
The predicted operating characteristics of the bandpass filters from the PSpice simulations are:
(a) / Value / Units / (b) / Value / Unitsfo / Hz / fo / Hz
f / Hz / f / Hz
Avat fn=1 / Avat fn=1
Avat fn=2 / Avat fn=2
Avat fn=3 / Avat fn=3
The number of poles in the active filter circuit based upon the slope of the frequency response is: ______.
Measurements
The first three Fourier components in the frequency spectrum of the square wave outputted by the Velleman function generator are:
Square Wave at f = 800 Hzand amplitude of 2V peak-to-peak / Percent Deviation from Calculated Values
Frequency (Hz) / Magnitude (dB) / Frequency / Magnitude
n = 1
n = 2
n = 3
Bandpass filter with fo = 800 Hz
The measured magnitudes and frequencies of the first three Fourier components of the square wave at the active filter output are:
Active Filter (fo = 800 Hz) / Percent Deviation from Calculated ValuesFrequency (Hz) / Magnitude (dB) / Frequency / Magnitude
n = 1
n = 2
n = 3
Qualitatively, thevoltage of the output of the active filter (fo = 800 Hz) as a function of time appears to be ______. Provide an explanation any distortions and include statements about how well the filter met the specifications stated in step 1.
Bandpass filter with fo = 2.4 kHz
The measured magnitudes and frequencies of the first three Fourier components of the square wave at the active filter output are:
Active Filter (fo = 2.4kHz) / Percent Deviation from Calculated ValuesFrequency (Hz) / Magnitude (dB) / Frequency / Magnitude
n = 1
n = 2
n = 3
Qualitatively, the voltage of the output of the active filter (fo = 2.4kHz) as a function of time appears to be ______. Provide an explanation any distortions and include statements about how well the filter met the specifications stated in step 1.
Conclusions
Explain why a higher order active filter would be desirable when used as a square wave-to-sine wave converter.