LOW-PASS FILTER, CIRCUIT FOR PLL

PROBLEM TO BE SOLVED: To provide the low-pass filter for PLL which can effective remove a frequency-divided signal component and a step frequency component included in an error voltage without exerting any influence on loop characteristics of a PLL. SOLUTION: The low-pass filter circuit is connected between the output of a phase comparator of a PLL of an electronic tuner and the input of a digital voltage-controlled oscillator and is equipped with low-pass filter parts 2 and 4 which removes the phase comparison frequency component outputted from the phase comparator and an active low-pass filter part which removes the phase noise (step frequency) component of the digital voltage-controlled oscillator; and the active low-pass filter part consists of a transistor 1 for voltage conversion and a negative feedback circuit 3 which is connected to the transistor 1 for voltage conversion and has frequency selection characteristics.