Mutchus

This simple and low pass  notch filter circuit. A variable notch filter with both high and low pass filters. Circuit Diagram: Notes: At first glance this circuit looks fairly complex, but when broken down,can be divided into high pass and low pass filter sections followed by a summing amplifier with a gain of around 20 times. Supply rail voltage is +/- 9V DC. The controls may also be adjusted for use as a band stop (notch) filter or band pass filter.

Description An all-pass filter is that which passes all frequency components of the input signal without attenuation but provides predictable phase shifts for different frequencies of the input signals. The all-pass filters are also called delay equalizers or phase correctors. An all-pass filter with the output lagging behind the input is illustrated in figure. Circuit Diagram The output voltage v out of the filter circuit shown in fig. (a) can be obtained by using the superposition theorem v out = -v in +[ -jX C /R-jX C ]2v in Substituting -jX C = [1/j2∏fc] in the above equation, we have v out ­= v in [-1 +( 2/ j2∏Rfc)] or v out / v in = 1- j2∏Rfc/1+ j2∏Rfc where / is the frequency of the input signal in Hz. From equations given above it is obvious that the amplitude of v out / v in is unity, that is |v out | = |v in | throughout the useful frequency range and the phase shift between the input and output voltages is a function of frequency. By interchanging the positions ...