band pass filters

Thread Starter


Joined Apr 17, 2010
Hi , I am designing a circuit that has a low pass filter, high pass filter and band pass filter. So far i gotten the low and high to work for the most part. They are individualy connected to leds. The low pass is supposed to come on at 100Hz, high pass at 10kHz, and band pass at 1k. The band pass is giving me trouble it deos not come on when it is supposed to. Attached is a copy of the circuit. Any ideas or help would be greatly appreciated.



Joined Dec 20, 2007
On your extremely simple bandpass filter, if the source has a very low impedance then frequencies above 14,500Hz are passed, frequencies below 14,500hz are cut, frequencies below 107Hz are passed and frequencies above 107Hz are cut so it doesn't work.

If you re-calculate resistor and capacitor values to cut frequencies below 1kHz and cut frequencies above 1kHz then its output at 1kHz will be very low.

Look in Google for Multiple Feedback Bandpass Filter.

Your extremely simple lowpass and highpass filters also seem to have the wrong values.