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DIY simple band-pass filter

This filter was designed to filter the 1kHz frequency of the telemetric signal from environmental noise. The filter itself is straightforwardly built with acceptable electronic parts worldwide. This filter can be used in any circuit because of its simplicity.

BC847_filter.PNG

The circuit contains a minimal amount of parts, including one general-purpose NPN transistor with coefficient 50…70 and more. Such filter blocks may be connected in series directly one to another(second IN first OUT). This way, filter gain may increase up to 1,2…2.

Bellow is a filter transfer function that consists of four cascade-connected filter nodes:

BC847_filter_characteristics.PNG

As you can see in the picture, filter level -3dB is at ±250Hz from 1kHz. While at ±350Hz, it reaches -6dB attenuation.

Filter drains about 0.5mA of current when three nodes are connected in series.

2 Comments:

  1. I am transmitting the output from a microcontroller. The signal received appears to have a great deal of noise introduced. The baud rate of the transmitted signal is 2400. I am looking for a circuit that can filter the noise on the output of the RF receiver . THANKS!

  2. I would like to know the calculations involved so it is possible to implement the filter with other frequencies, thank you!

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