RC Filter Continous Waveform

Discussion in 'The Projects Forum' started by iimagine, Dec 5, 2013.

  1. iimagine

    Thread Starter Active Member

    Dec 20, 2010
    I need a little help here. I want to implement a Highpass filter that outputs a continuous voltage waveform. I have experiment this on Falstad's java sim and able to get it to produce what I want, somewhat... The problem is how do I simulate this in LTSpice? Is there any problem(s) with this circuit of mine? Are there any other way of doing it?

    PS: I prefer using discrete components if possible since I want to learn more about them.

  2. crutschow


    Mar 14, 2008
    That circuit has no bias current for the transistor base and will clip the waveform, acting more or less like a half-wave recitifer.

    If you just want a filter, why did you add the transistor?

    What filter characteristics do you want (corner frequency, rolloff rate, input/output impedance, gain, etc.)?
  3. iimagine

    Thread Starter Active Member

    Dec 20, 2010
    You are right, I cant use it the way it is. The reason that use the transistor is to amplify the voltage from an input audio signal source

    Well I'm planning on using this output waveform to control a PWM LED brightness, from an audio line in, a better colour organ if you will :)

    I dont know much about filtering, so if you have better ways please show me how

    I have updated the circuit to include the buffer stage, please advise

    Edit: The circuit is taken from a 3 band colour organ founded on the net. I just modified it a bit to suit my need