Adaptive phase locked loop for video signal sampling

Presents a new BiCMOS adaptive phase locked loop (PLL) circuit for a video signal sampling system. This circuit significantly decreases the acquisition time of a standard second-order charge-pump PLL without affecting its noise performance in the locked state. The adaptation consists of tuning the bandwidth of the loop filter during signal acquisition. Tuning is achieved by adjusting the transconductance of an operational transconductance amplifier (OTA). The adaptive algorithm is reviewed for the general case of PLLs in terms of the circuit components and system requirements