There is something I'm struggling to understand about passive RC filters: When considering a simple low pass RC loop, what exactly is the gain/output at DC and low frequencies? I've been assuming two possible events:
The input charges the capacitor, setting the output equal to input as soon as the capacitor is charged;
Due the high reactance of the capacitor at DC and low frequencies, the current, the capacitor can be ignored, and thus there is a small drop across the resistor, which will depend on the load resistance and current.
However, both seem to contradict each other, particularly as to whether or not there is an actual voltage drop across the resistor.