A phase locked loop (PLL) circuit is provided to operate in a broad band, including
two separate loops one of which is for feed-back of an output from an oscillator
to the same oscillator through its associative proportional control unit and the
other of which is for feed-back of an output of an oscillator to the same oscillator
via an integral control unit. The proportional control unit is arranged to control
an output frequency of the oscillator and is operable to generate a control signal
based on a difference between input and output signals. The integral control unit
is arranged to control the phase of an output signal of the oscillator to thereby
generate a control signal based on a phase difference between input and output signals.