| 摘要 |
PURPOSE:To prevent abnormal oscillation at a UHF band, by constituting a tracking capacitor of two capacitors in a tuner of a TV receiver, connecting one capacitor to the each side of an oscillation transistor (TR), and the other to earth side of a resonance circuit. CONSTITUTION:An oscillation circuit provided with a TR1 of common base is oscillated in the frequency determined with a resonance circuit 8 through the oscillation of the feedback operation of a capacitor 2, and tuned to a frequency required for a tuner of a UHF band with a varactor diode 7. A tuning tracking capacitor is constituted with a capacitance CTj formed at the earth side of a tuning diode and a capacitance CTb formed at the base side of the TR1. In making the oscillation circuit flat, an inductance 9 is increased and a hysteresis phenomenon is caused in the oscillating operation, but the tracking capacitance CTj is made small to prevent the hysteresis phenomenon and the decreased capacitance is compensated with the tracking capacitance CTb to realize normal tracking. |
