Sallen and Key Bandpass filter

[cps13]

Hi,

I have the following question, which I need some fundamental help with to get going:

Design and PSPICE model a bandpass filter of ‘Sallen and Key’ topology and having the following characteristics: fo ~ 3.3kHz, Q ~2.2. Verify your design by means of a Bode plot.

From my learning material, and what I can find online. There appears to be a specific circuit for a Sallen & Key bandpass filter.

My questions are:

1) Should I be cascading a low-pass and a high-pass filter still to create the 'band' for the desired circuit? Everything online and in my material doesn't suggest so, but I thought fundamentally this is what a band pass filter is?

2) The question specifies fo as 3.3kHz. I understand this is the output frequency, but I don't understand how this relates to a bandpass filter? Is 3.3kHz on my bode plot where I should see -3dB (0.707) on my slope?

3) I know the fo value and the Q ratio from the question. However, i'm not sure how to get started to find my RC values.

Thanks,

 

[crutschow]

fo is the center frequency where the gain is nominally 0dB (1) for an op amp configured as a gain-of-one follower.
You can do the filter with one op amp, as shown here.