LCR Power input filter: Input source models a battery or other non-ideal voltage source. The voltage source is supposed to only have DC component, but an AC component at a specific frequency is set to model noise. The resistance is low because its purpose is to take in account inductor resistance only; an external resistor is not needed and increases cost. The LRC filter is a low pass filter. The math (not taking in account R) returns a cutoff frequency (-3db point) of about 1.6 MHz
which is: f_cutoff = 1 / (2*pi*sqrt(L*C)); Additionally, the greater the R, the more damping, and the bode plot adjusts accordingly. This filter can be useful as a first stage in a power electronics circuit and may work well to utilize before linear or switching supplies.
