Phase-locked loop circuit

摘要

A phase-locked loop circuit has an output amplifier ( 27 ) and a main feedback path from the output of the output amplifier ( 27 ). A subsidiary feedback path is provided directly from the output of the circuit's VCO ( 32 ). At the start of operation, the output amplifier ( 27 ) is disabled and the subsidiary feedback path is used until lock is achieved. Then the output amplifier ( 27 ) is enabled and the main feedback loop is used. This avoids spurious outputs from the outer amplifier while to loop locks.