| 摘要 |
PROBLEM TO BE SOLVED: To smooth a voltage waveform of an output clock that is changing and to make the scale of the digital voltage controlled oscillating circuit. SOLUTION: The digital voltage controlled oscillating circuit consists of a ring oscillator circuit 1 and a decoder circuit 3, and a phase locked loop PLL circuit consists of a voltage controlled oscillator circuit and a phase comparator 2. The phase comparator 2 compares an external reference frequency with an output frequency and gives phase difference information to the decoder circuit 3. The decoder circuit 3 gives a switching signal to the ring oscillator circuit 1 according to the phase difference information. The ring oscillator circuit 1 consists of CMOS inverter circuits I1-In and 1st and 2nd variable resistor sections. Selecting either of the variable resistor section smoothly changes an output frequency of the ring oscillator circuit.
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