| 摘要 |
An oscillation output generating circuit outputs a voltage V0 as an oscillation output, and a first comparing circuit compares V0 with a constant voltage V1, while a second comparing circuit compares V0 with a constant voltage V2 (<V1). In response to outputs from the first and second comparing circuits, a state maintaining circuit controls the raising/dropping of V0 through the oscillation output generating circuit. When a synchronizing pulse for synchronous oscillation is not inputted, self-advancing oscillation is started, and synchronous oscillation is started otherwise. When the synchronizing pulse is in an active state, a nullifying circuit inhibits transmission of an output from one of the first and second comparing circuits to the state maintaining circuit, whereas the nullifying circuit allows the above transmission when the synchronizing pulse is in an inactive state. Further, when the synchronizing pulse has shifted from the active state to the inactive state, an edge trigger circuit switches an output signal from the state maintaining circuit between a dropping signal and a rising signal.
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