frequency to voltage converter?

Discussion in 'Homework Help' started by graemewhite88, Apr 8, 2009.

  1. graemewhite88

    Thread Starter New Member

    Apr 8, 2009
    we have been set a question at college to design a frequency to voltage converter. we have been trying to do this for over a month now but have been unsuccessful. any help would be appreciated

    input = 20hz - 20khz
    output = .25v/khz

    please please please help.

    edit: we also cant use dedicated IC's to do this, just basic op-amps, monostables etc.
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    How about this rather simplistic approach ...

    Edge trigger a 25uS, 10volt monostable circuit with the 20-20kHz signal.

    Use a LPF to extract the mean of the monostable output.

    At 20Hz mean value = 10 x 25e-6 x 20 = 5mV

    At 20kHz mean value = 10 x 25e-6 x 20e3 = 5V

    Each output complies with the 0.25V per Khz spec.

    Designing the filter is probably the more challenging part.
  3. omarara

    New Member

    Mar 31, 2009
    I didn't do math for this circuit but this is the right one :) as the circuit doesn't need any input but only small trigger and the output will be fixed till you send another trigger
  4. nigelwright7557

    AAC Fanatic!

    May 10, 2008
    A phase locked loop will perform this function.
  5. dsp_redux

    Active Member

    Apr 11, 2009
    Would one HPF and one LPF in parallel do the job? You put at the end of each filter a FET and give the right voltage to the output?