Patent ID: 7719370

Claim:
A voltage controlled oscillator that is a different ring oscillator type voltage controlled oscillator, comprising: a plurality of differential delay elements that each have a pair of differential input terminals, a pair of differential output terminals, and a bias input terminal, with clock signals of a mutually reverse phase input to the pair of differential input terminals; a phase detection portion that is connected to the differential output terminals of one differential delay element for detection among the plurality of differential delay elements, detects an abnormal oscillation by comparing an output voltage of the differential output terminals and a reference voltage that is set to a voltage that detects an abnormal operation and outputs a detection signal; a cross-coupled circuit that is provided at each of the differential delay elements and connected to the phase detection portion, and, when the detection signal is input, amplifies the potential difference between the pair of differential output terminals; wherein by connecting in cascade the plurality of differential delay elements at the differential input terminals and the differential output terminals and controlling the amount of current that flows to the differential delay elements by a bias voltage that is impressed on the bias input terminal, the voltage controlled oscillator controls the delay amount of the clock signal.