A phase locked loop (PLL) is use in a radio communication system such as a frequency mixer, a carrier frequency and the like. The phase locked loop (PLL) includes a phase/frequency detector for comparing a phase/frequency of a reference signal and a feedback signal. The phase/frequency detector includes: a NAND gate logic circuit for NANDing a first signal and a second signal to output a NANDed signal; a first latch unit for latching the NANDed signal and outputting the first signal in response to a reference frequency; and a second latch unit for latching the NANDed signal and outputting the second signal in response to a feedback frequency. The phase locked loop (PLL) further includes a filter controller for changing a bandwidth of a low pass filter in response to an output signal of the phase/frequency detector.