| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage controlled oscillator which can easily generate the oscillations by using a ring oscillator, a 1st bias circuit including a replica circuit and a differential gain increase circuit which increases the differential gain of a differential amplifier. SOLUTION: The external control voltage VC is given to a ring oscillator 1 and a bias circuit 2, and the reference voltage VR is given to the circuit 2. The clock signal produced by the oscillator 1 has a cycle double as much as the sum of delay time of a differential buffer, and the delay time of the differential buffer varies according to the voltage VC. Thereby the frequency of the clock signal varies according to the voltage VC. At the same time, a minute potential difference is caused between an output node Nnc and an inverted output node Nnd of the differential buffer. Then a differential gain increase circuit 3 supplies a current in the direction where the potential difference is increased. As a result, the differential gain of the differential buffer of the final stage is increased and the oscillator 1 can easily generate the oscillations. |
