op amp based band pass filter

Hi,
I would like to know the design of center frequency selectable type band pass filter with operation amplifier.

Here is a tunable bandpass filter, using a single op amp. I found the schematic on the internet somewhere.

The capacitor values are at a ratio of 3:1. These values provide an adjustable center frequency from about 400 to 900 Hz.

Hi Brad,
What's the value of the potentiometer in that circuit?
Thanks- Godfrey

10k. (Careless of me not to label it.)

It is in the normal position for adjusting gain. As a result, gain will be different at different center frequencies.

Thanks. Interesting circuit. I noticed in simulation it's actually a high-Q low-pass rather than a true bandpass.

It's still not clear what the OP's requirements are anyway as he didn't mention the frequency range of interest. This is posted in the RF section of the forum, but opamps aren't normally used at RF, IMHO.