AC Coupling Arduino PWM Output Over varying Frequencies

Thread Starter


Joined Nov 12, 2020
The load on the output is 100ohms. The frequency will vary through the full range of the arduino. My simetrix simulations shows it should work using a 100uF capacitor biased by a 1Mega ohm resistor, but in theory it doesnt. If someone knows the values of the components to use or another method it would be much appreciated.

Audioguru again

Joined Oct 21, 2019
If an Arduino has a peak output of 5V with no load but reduces its output to 3V with a 100 ohms load then its output resistance is
too high for a 30mA PWM load.
100uF and a 100 ohms load has a -3dB cutoff frequency of 16Hz. The level will be 0.707 of much higher frequencies.


Joined Oct 28, 2019
The output of the Arduino is PWM as you correctly state. It firstly needs to be turned into an AC waveform by a filter (RC). This may not be very effective if the range of output frequency is more than an octave or so. (Its a compromise between generating a sine wave vs response time to do it) . Once you get an AC output put it through a non inverting buffer. This disengages any output load effects on the filter.