An object is to provide a PLL having a wide operating range. Another object is to provide a semiconductor device or a wireless tag which has a wide operating range in a communication distance or temperature by incorporating such a PLL. The semiconductor device or the wireless tag includes a first divider circuit; a second divider circuit; a phase comparator circuit to which an output of the first divider circuit and an output of the second divider circuit are provided; a loop filter to which an output of the phase comparator circuit is supplied and in which a time constant is switched in accordance with an inputted signal; and a voltage controlled oscillator circuit to which an output of the loop filter is supplied and which supplies an output to the second divider circuit.