Patent ID: 7911282

Claim:
A voltage-controlled oscillator, comprising: a plurality of delay cells cascade connected, each of the delay cells receiving a differential input signal and outputting a delayed differential output signal, a delay time of the delay cells being controlled by a current to be supplied from a voltage-current conversion circuit, a differential output signal of a last stage of the delay cells being fed back as a differential input signal of a first stage of the delay cells so that the differential output signal has a reversed phase with an input of the first stage of the delay cells, in order to produce an oscillation frequency controlled by applying a voltage to the voltage-current conversion circuit, wherein each of the plurality of delay cells includes: a first buffer inverter which receives one of the differential input signal and outputs an other of the differential output signal; a second buffer inverter which receives an other of the differential input signal and outputs one of the differential output signal; a first latch inverter which receives the one of the differential output signal, and includes an output connected to an output of the first buffer inverter; and a second latch inverter which receives the other of the differential output signal, and includes an output connected to an output of the second buffer inverter, wherein the first latch inverter and the first buffer inverter receive a current produced from different voltage-current conversion circuits; and wherein each of the plurality of delay cells includes: a first voltage-current conversion circuit which supplies a first current to the first buffer inverter; a second voltage-current conversion circuit which supplies a second current to the second buffer inverter; a third voltage-current conversion circuit which supplies a third current to the first latch inverter; and a fourth voltage-current conversion circuit which supplies a fourth current to the second latch inverter.