| 摘要 |
In a VCO, the switching of capacitor charge control circuits between capacitor charging and discharging states is rendered responsive to the current demand of a first FET monitoring the potential across the capacitor. The source-drain path of a second FET, variable in conductivity in response to an external frequency control signal, is connected in the source circuit of the first FET, in parallel with the source-drain path of a third FET. The third FET is non-conductive during operation in the capacitor charging state, but is strongly conductive during operation in the capacitor discharging state. As a consequence, the threshold potential at which switching to the capacitor discharging state occurs varies in accordance with the control signal, while the threshold potential at which switching to the capacitor charging state occurs does not so vary.
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