| 摘要 |
PURPOSE:To start the oscillation synchronously with an oscillation control signal and to obtain an oscillation output having a constant phase by discharging the electric charge charged in a capacitor through a constant current source as soon as an oscillation control signal of a voltage controlled oscillator is used for the start of oscillation. CONSTITUTION:When a level of an input terminal 7 of an oscillation control signal changes from a Low to a High level, a transistor (TR) 8 is turned on, a TR 9 is turned off and the emitter voltage of the TR 9 gets higher. When the level of the oscillation control signal input terminal 7 changes from a high to a low level, the TR 8 is turned off and a current drawn by a constant current source 12 flows from the TR 8 to a capacitor 10. As a result, the capacitor 10 is discharged through the constant current source 12, the emitter voltage of the TR 9 is decreased and the TR 9 is turned on. The collector voltage of the TR 9 is decreased after the level of the oscillation control signal input terminal 7 changes from a high to a low level, the time when the collector voltage of a TR 6 gets higher is always constant and the oscillation is started synchronously with the oscillation control signal.
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