replacing to voltage reference

[us1710]

i am designing the pll. presently i am using ideal voltage and current sorces in bias. if these are replaced by voltage and current circuit, then what would be effect on performence of pll.
what things should be taken in consideration while designing reference circuit.

 

[suria3]

When replace the current source with actual transistor, you have to ensure the current flowing with the actual transistor is the same is per ideal source, if not your gain and dc point will be effected.