With a low-pass RC filter, since the maximum current when charging/discharging the capacitor is determined by the resistance value, attention must be paid to this resistance. When the initial charge of the capacitor is set to 0 the resistance becomes the load of the opamp and when the output current exceeds the opamp's current capacity distortion occurs. Also, if the resistance is small it is necessary to check the phase margin because the phase may turn due to the capacitance of the output capacitor, causing the opamp to oscillate.