Band Pass Filters


Posted on Feb 6, 2014

A band-pass filter is a circuit which is designed to pass signals only in a certain band of frequencies while attenuating all signals outside this band. The parameters of importance in a bandpass filter are the high and low cut-off frequencies (fH and fl), the bandwidth (BW), the centre frequency fc, centre-frequency gain, and the selectivity or Q


Band Pass Filters
Click here to download the full size of the above Circuit.

. There are basically two types of bandpass filters viz wide bandpass and narrow bandpass filters. Unfortunately, there is no set dividing line between the two. However, a bandpass filter is defined as a wide bandpass if its figure of merit or quality factor Q is less than 10 while the bandpass filters with Q > 10 are called the narrow bandpass filters. Thus Q is a measure of selectivity, meaning the higher the value of Q the more selective is the filter, or the narrower is the bandwidth (BW). The relationship between Q, 3-db bandwidth, and the centre frequency fc is given by an equation For a wide bandpass filter the centre frequency can be defined aswhere fH and fL are respectively the high and low cut-off frequencies in Hz. In a narrow bandpass filter, the output voltage peaks at the centre frequency fc. A wide bandpass filter can be formed by simply cascading high-pass and low-pass sections and is generally the choice for simplicity of design and performance though such a circuit can be realized by a number of possible circuits. To form a ± 20 db/ decade bandpass filter, a first-order high-pass and a first-order low-pass sections are cascaded; for a ± 40 db/decade bandpass filter, second-order high- pass filter and a second-order low-pass filter are connected in series, and so on. It means that, the order of the bandpass filter is governed by the order of the high-pass and low-pass filters it consists of. A ± 20...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Analog Multiplexer
    LED Christmas Star
    220 V LED Night light
    Automatic-video-switch
    Measure your stress level Tension meter Schematic Diagram
    how to make simple frequency counter
    Digital Radar Speedometers
    Rectifier/filter circuit Semiconductors
    Novice CW Transmitter
    UV-3R
    Eliminate hum instrumentation amplifier INA101 circuit



    Top