PWM DAC Woodward Solutions

I recently read an article by Stephen Woodward discussing different implementations of 2nd order low pass filters here: https://www.edn.com/cancel-pwm-dac-ripple-with-analog-subtraction-revisited/ In these designs an inverted PWM signal (eg. A microcontroller’s complementary output) is used to cancel some ripple Top left is a typical single pole RC low-pass filter: -high ripple +short settling time Bottom left is a double pole RC low-pass filter: +low ripple -longer settling time Top right is a double pole RC low-pass filter (Woodward’s design): *same effect as the typical double pole +low ripple -longer settling time Bottom right is another double pole RC low-pass filter (Woodward’s design again): *inbetween results of these other filters +low ripple (slightly worse than double pole) +short settling time

published 2 years ago