| 摘要 |
PURPOSE: A high-speed PLL(Phase Locked Loop) circuit is provided to perform continuously an oscillating operation though an input voltage of 0 volt is applied. CONSTITUTION: A VCO(Voltage Controlled Oscillator) circuit(20') is formed with a VCO bias portion(22') and a VCO output portion(24'). The VCO bias portion(22') outputs bias voltages(VBIAS1',VBIAS2') to the VCO output portion(24') in response to a control signal(VCONTROL) when a control signal is in an active state. The VCO output portion(24') generates an output signal(fo) in response to the bias voltages(VBIAS1',VBIAS2'). The VCO bias portion(22') is formed with 4 PMOS transistors(MP10,MP12,MP14,MP16), 5 NMOS transistors(MN10,MN12,MN14,MN16,MN18), and a resistance. The VCO output portion(24') is formed with an operation amplifier, a VCO cell, and a ring oscillator.
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