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DIY simple band-pass filter

2015-01-12 21:10  
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This filter was designed to filter 1kHz frequency of telemetric signal from environmental noise. Filter itself is very simple built with acceptable electronic parts worldwide. This filter can be used in any circuit because of it’s simplicity.

BC847_filter.PNG

 

Circuit contains minimal amount of parts including one general purposes NPN transistor with coefficient 50…70 an 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 filter transfer function which 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.


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