*L*=inductance of choke

*R*_{DC}=DC resistance of choke

*C*=capacitance of filter capacitor.

Ideally, the resonance should be critically damped (*Q*=0.5), which can be achieved by adding external series resistance to the choke. Strictly, the load resistance across the capacitor also damps the resonance, and this may be transformed into a notional extra choke series resistance using:

${R}_{\text{notional}}=\frac{L}{C{R}_{\text{load}}}$

However, the damping effect of the load resistance is usually negligible. Even worse, a series voltage regulator is a constant current, or infinite, AC load to the smoothing circuitry, so it adds no damping whatsoever.

*A typical traditional example*: A choke input ...

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