integrated loop filter ?

Dear all :
We are doing PLL design, The bw is about 30kHz. How do we integrated loop filter. Becasue teh Capacitor is very large, and good method do scaler or any document about this ?


mitgace

have some formulae

1) Capacitance multiplier using a bipolar with a smaller capacitor on the base. Looks like a much larger capacitor on the collector. Not quite like this, but here is one example:
http://en.wikipedia.org/wiki/Capacitance_multiplier

2) Realize that the open loop "bandwidth" of a PLL is where the gain crosses zero on the frequency axis. You can get your bandwidth to look like 30 KHz by making the integrator capacitance large. You could get the same bandwidth with a smaller capacitance and less loop gain. For instance, if you need a 1000 pf capacitor to get 30 KHz for a given loop gain, if you put in a 10:1 voltage divider before the varactor diode then the 30 KHz bandwidth can be had with only a 100 pF capacitor. In discrete circuits, I bypass the 10:1 voltage divider with an inductor so the DC tuning range is still to the supply rails, maybe you could do the same with some sort of op amp circuit where the DC coarse tune goes thru one path and the AC 30 KHz bandwidth goes through another path.