| 摘要 |
PROBLEM TO BE SOLVED: To provide a ring oscillator that can adopt a low power supply voltage with excellent stability in the center frequency and attain frequency control with excellent linearity and to provide a PLL(phase locked loop) circuit employing the ring oscillator for its voltage-controlled oscillator. SOLUTION: In the ring oscillator comprising active bandpass filters 11 to 14 connected in a ring which output a plurality of period signals whose frequencies are equal to each other but whose phases differ from each other, the bandpass filter 11 of a first stage comprises two trans-conductance circuits 111, 112 in which the circuit 111 is directly connected to a next stage as one component in ring connection and RC parallel circuits 113, 114 driven by the trans-conductance circuits 111, 112. Other bandpass filters 12 to 14 are similarly configured to the filter 11. |
