A PLL is set up so that its VCO free-runs at 8.9 MHz. The VCO does not change frequency unless its input is within plus or minus 75 kHz of 8.9 MHz. After it does lock, the input frequency can be adjusted within plus or minus 120 kHz of 8.9 MHz without having the PLL start to free-run again. The tracking range of the PLL is:
A) 240 kHz
B) 75 kHz
C) 120 kHz
D) 150 kHz

Question

Quizplus · Accepted Answer

The tracking range of a Phase-Locked Loop (PLL) is defined as the range of input frequencies over which the PLL can maintain lock once it has achieved lock. Given that the PLL can adjust within plus or minus 120 kHz of 8.9 MHz without losing lock, the total tracking range is 120 kHz + 120 kHz = 240 kHz.

A PLL Is Set Up So That Its VCO Free-Runs