| 摘要 |
PURPOSE: A voltage controlled oscillator is provided to be insensible to a variation of a power supply voltage, and to obtain a constant output regardless of an operation frequency. CONSTITUTION: A voltage controlled oscillator comprises a bias part, a delay part and a buffer. The bias part generates a bias voltage(Bp) in inverse proportion to a variation of an externally applied bias voltage(Bn). The delay part has serially connected delay cells, and the buffer forces an output to have a duty rate of 50% regardless of an operation frequency. Among the delay cells, a first delay cell is connected to receive output signals of a delay cell of the last state. Each of the delay cells consists of four PMOS transistors(PM2-PM5), three NMOS transistors(NM3-NM5), two input terminals(In,Ip), two output terminal(Op,On) and two control terminals(Bn,Bp). The transistors(PM2,NM3) are connected in series a power supply voltage and a drain of the transistor(NM5) whose source is grounded. The transistors(PM5,NM5) are connected in series the power supply voltage and the drain of the transistor(NM5). The gate of the transistor(PM2) is connected to the output terminal(Op), and the gate of the transistor(PM5) is connected to the output terminal(On). The gates of the transistors(NM3,NM5) are connected to the input terminals(In,Ip), and the gate of the transistor(NM5) is connected to the control terminal(Bn). The transistors(PM3,PM4) are connected in parallel with the transistors(PM2,PM5), respectively, and the gates of the transistors(PM3,PM4) are connected in common to the control terminal(Bp).
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