The effect of loop gain in PLL

Salam (in farsi = Hello)
Its main function is producing proper control signal in loop.
it reduces noise in loop, and filters high frequency unwanted components of signal for example in 2f0 and produces proper control signal for VCO

Visit:
http://ocw.mit.edu/OcwWeb/Electrical...otes/index.htm

Please find lecture material below:
21 Overview of Phase-Locked Loops and Integer-N Frequency Synthesizers (PDF)
22 Noise in Integer-N and Fractional-N Frequency Synthesizers (PDF - 1.0 MB)
23 Design of Fractional-N Frequency Synthesizers and Bandwidth Extension Techniques (PDF - 2.4 MB)