Notch Filter & Bandpass Filter: Creating Interchangeable Filters Through Electronics
What's this project about?
This project is to create two adjustable filters that can be switched smoothly with two dual gang potentiometers. The filters of the project are notch and bandpass filter, it is controlled by a low pass and high pass filters. The main goal is to create filters that can cut certain frequency. To make it user friendly, it is also designed with sliders, so it is easier to control.
What does each part of the circuit do?
My circuit is essentially composed of five main sections (figure below). The first section (A) includes the input and a buffer. The buffer can solve a lot of impedance issues within the circuit and it an turn the impedance to a lower value as its output.
The second section (B) is a bandpass filter with two dual gang potentiometers. The dual gang potentiometers allow me to simplify my circuit and adjust the notch and bandpass filter with the same sliders. The bandpass filter is composed of a low pass filter and high pass filter. first, the signal goes through the low pass filter. Then, it goes through the high pass filter. with the signal being overlapped by two filters, it generates a bandpass filter. The adjustable sliders allow it to change the cutoff frequency.
The third section (C) is a simple notch filter with the same potentiometeres from B. The notch filter is built in parallel to allow the signals to be attenuated. In a way, it works like a band-stop filter depending on the range of the sliders. With my adjustable sliders, the notch filter gives the signals that were removed by the bandpass filter.
The fourth section (D) is an inverting summing amplifier to achieve a unity gain. In a simpler way, the summing amplifier can add two filtered signals together with equal gains before sending them to the output. The fifth section is an output that ensures my earphones/speakers are protected with the capacitors and resistors.