PLL

[hatemt]

1-Why does the loop bandwidth need to be much less than the reference frequency in order to be able to use basic feedback control theory and Laplace transforms in PLL analysis?

2-How does the leakage current in a charge pump phase detector affect the performance of a PLL

[garylsmith2k]

As to question 2:

The charge pump leakage is converted to voltage by the loop filter resistors. This spurious voltage is then applied to the VCO generating, among other things phase noise, which we always seek to minimize.

Gary