Active loop filter or Passive loop filter?

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We can see there are two classificatons of loop filter in PLL design.
We often use the passive loop filter for our design, but the active filter
still exists. I don't know why we use active filter, what's the advantage
of it? Anybody has the experience of this?
 

1. It can place the poles and zeros closer to DC than a passive filter, given the constraints on the component values.

2. It can be used to increase the loop gain of the overall circuit.
 

One of the great advantages of the active filter is when the charge pump has a low compliance range, and u need a larger one to let ur VCO work on the desired range. So u use an active filter to eliminate the dependence between the charge pump compliance range and that of the VCO control voltage.
 

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