power supply Inductive choke with bypass capacitors

Posted on Feb 5, 2014

Using an inductor inline and a decoupling capacitor it`s creating essentially a series LC circuit. Now one of the properties of LC circuits is they have a resonant frequency. I modeled a LC circuit with an attached purely resistive load to simulate what the circuit did under different kinds of loads: As expected high frequency noise is very effectively reduced (if I`m not mistaken, outside the peak region it should decay at 40 dB per decade).

power supply Inductive choke with bypass capacitors
Click here to download the full size of the above Circuit.

However, there is that ominous spike at around 20 kHz where noise is actually being very effectively amplified from the resonant frequency. Is this typically not a factor when it comes to regulating power to a board Why isn`t the RC filter created using bypass capacitors enough Is it because the capacitor size required for an effective RC filter is too high Or am I missing something in my model

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