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 / Value
C / 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 with
fo = 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 / Units
fo / 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 Hz
and 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 Values
Frequency (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 Values
Frequency (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.