| 摘要 |
PURPOSE:To obtain a clear UHF picture image free from any disturbing phenomenon, by applying the backward bias to the switch diode used for the input circuit of the VHF tuner part and at the UHF receiving time by means of the power source to be supplied to the VHF mixer. CONSTITUTION:The voltage is applied to mixer 7 which is used for the IF amplifier at the UHF receiving time, and then the backward bias is applied to switch diodes 2 and 3 via resistance 19. Thus the vias voltage can be controlled via resistances 4, 5, 16, 17 and 19 each. And the disturbance property can be reduced by applying the deep backward bias voltage at the receiving time of UHF and even though the signal of large amplitude may be transmitted to the VHF input terminal. As a result, a clear UHF picture image can be obtained with an disturbing phenomenon. |
