Oscillating circuit

Abstract

Abstract PURPOSE:To oscillate the VHF band and the UHF band, by using a switching element to switch a feedback capacity, which determines the frequency character istics of a fixed tuning element and a negative resistance, in a local oscillating circuit in the tuner of a TV receiver. CONSTITUTION:In case of oscillation of a frequency of the VHF band of the TV, a negative voltage V pin is applied to turn on a pin diode (PD) 47 and turn off a PD39. At this time, the capacity between the collector and the emitter of a transistor (TR) 51 becomes the sum of a capacitor (C) 53 and a C46, and the negative resistance of an amplifying circuit expands throughout the VHF band. An inductance (L) 38 is connected to a varactor diode (VD) 41 to tune in the VHF band. In case of oscillation of the UHF band, a positive voltage Vpin is applied to turn off the PD47 and turn on the PD39. The capacity between the collector and the emitter of the TR51 becomes the capacity of the C53, and the negative resistance of the amplifying circuit expands throughout the UHF band. Ls 37 and 38 are connected in parallel to the VD41 to tune in the UHF band.

Inventors

• 👤 Shigeo Fujimori
• 👤 Toshiki Tomisaka

Bibliographic Details