Distortion in triangular waveform

Discussion in 'The Projects Forum' started by Marie, Jan 16, 2008.

  1. Marie

    Thread Starter Member

    Nov 20, 2007

    I'ld need help about the generation of a triangular waveform. I've designed a schmitt comparator to generate a square wave and i use an integrator to generate the triangular waveform.

    The circuit work in simulation. However, in practice, there is a distortion in the falling edge. I've used TL072 as opamps and the frequency is about 5kHz.

    I've attached a schematic of the circuit i used plus the resulting waveform on the oscilloscope.

    I'ld like to know if there is a way to get a clear waveform. I've tried with other ICs: LM747 and LM324 put the waveform is worse.

    Thank you
  2. Audioguru


    Dec 20, 2007
    I think your resistor values are too low. Use a 0.01uF capacitor and 10 times the resistor values.
    With your very low supply voltage the opamp cannot pump enough current into the resistors and capacitor at the peak of the triangle wave. Then when it changes direction, the hysteresis helps the waveform.
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    If the signal is still distorted with 6.16K and 0.01uF, you can try going another order of magnitude to 61.6K and 0.001uf. The TL-072 opamps are fet inputs so the higher input resistance should be OK.

    You may have to lower the value of the 8.2K resistor and accept a smaller peak-to-peak triangle wave. As audioguru has indicated, the +5V/-5V power supply is a bit low since the TL-072 is not a rail-to-rail opamp.

  4. Marie

    Thread Starter Member

    Nov 20, 2007

    Thanks a lot. It does work out with the new resistor and capacitor values.