| 摘要 |
PURPOSE:To perform a good AFC operation, by performing the control so that the sensitivity of the phase detecting circuit is enhanced when the power source voltage shows a prescribed value or less. CONSTITUTION:In the low-voltage region before power source voltage VCC rises sufficiently, bias voltages VB1 and VB2 formed by dividing power source voltage VCC are near to each other, and currency flowed to resistances R1 and R2 provided in the collector of transistor Q1 become small. For the purpose of compensating lowering of the phase detection sensitivity caused as the result, transistor Q3 if turned on by the output of voltage detecting circuit 1 to short-circuit resistance R1. |
