| 摘要 |
PURPOSE:To eliminate a failure of a varactor diode in a VCO caused by a self- bias voltage by using an emitter follower to which a constant current is applied from a constant current supply as a frequency control voltage input circuit to the VCO. CONSTITUTION:A prescribed value of a reference signal inputted from a terminal 54 is mixed with a oscillating output signal of the VCO11 at a phase comparator 6 and detected synchronizingly and a phase error signal corresponding to the phase difference of both signals is generated and amplified at an AC amplifier 7, inputted to an emitter follower Q2 and further, amplified by a DC amplifier 8 and inputted to a lag filter 9, both signals via the AC amplifier 7 and the DC amplifier 8 are synthesized to produce a frequency control signal to the VCO11. In the emitter follower Q3, a prescribed frequency control voltage is outputted in response to the excitation of a frequency control signal inputted via the lag filter 9 and applied to the varactor diode of the VCO11. A specified current, nearly several mA, flows to the varactor diode and no self-bias voltage is generated. |
