| 摘要 |
PURPOSE:To shift the working point of a diode and to avoid an AFC(automatic frequency control) pull-in malfunction by impressing the AFC voltage and the DC bias voltage to the anode and cathode sides of a voltage variable capacity diode respectively. CONSTITUTION:A voltage variable capacity diode 92 to which the AFC voltage is applied functions to control the oscillation frequency of an oscillation circuit 18. The anode side of the diode 92 is connected to a reference potential point. At the same time, the AFC voltage given from a terminal 87 is impressed to the anode of the diode 92. While a prescribed level of DC bias voltage is impressed to the cathode side of the diode 92 from a DC power supply terminal 85. In such a constitution, the working of an AFC circuit can be set within a range where the good linearity is obtained for the AFC characteristics. In this way, an AFC pull-in malfunction is prevented. |
