# Electronic – Simulating and Building a Multiple Feedback Band-Pass Filter

bandwidthfilteroperational-amplifiervoltage

I have a distorted signal, and only want to allow frequencies between 95kHz and 105kHz. The input voltage is at 300mV peak to peak.

Thus, I need a Pass Band of 10kHz and a Central Frequency at 100kHz.

I was reading through various analogue electronics books to find out some commonly used variations and topologies and decided to go for the Multiple feedback filter.

I will be using this circuitry:

According to this document:

This circuit is widely used in low Q (<
20) applications. It allows
some tuning of the resonant frequency, F
0
, by making R2 variable.
Q can be adjusted (with R5) as well, but this also
change
s F
0
.

I then proceeded by follwoing the equations on that same document, or else on the book, Op Amp Applications Handbook.

My calculations and working is listed below:

First, we must determine the centre frequency, bandwidth, and Q.

The Q is too high to use separate high- and low-pass filters, but
sufficiently low so that a multiple feedback type may be used.

Before actually building this circuit I want to be able to simulate it. Here is my circuit implemented on Proteus software.

And this is the respective frequency response:

It may not be clearly visible, I apologize, but the center frequency is only at 63kHz.

At 100kHz the max output voltage swing is only 1V peak to peak, and thus I am keeping my gain levels, low. (AV = 2)

I followed the instructions, but clearly I am doing something wrong.

How can I get an actual center frequency of 100kHz, and what am I doing wrong?

Any tips and/or suggestions would be appreciated.