VHF tuner
 In a VHF tuner, feedback capacitance between the emitter of a local oscillating transistor and the ground in a local oscillator is changed at the low band receiving state and high band receiving state by controlling a switching diode connected in series to a capacitor for feedback capacitance and, a mixer is installed to mix the output of the local oscillator and high frequency input. For an improved mixer biasing circuit, the switching diode in series connection to the capacitor for feedback capacitance is connected to one terminal of a mixing FET in the mixer, and changing of the feedback capacitance in the local oscillator is accompanied by changing of working current of the mixing FET in the local oscillator. 
Alps Electric Co., Ltd.
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inventional inventional inventional
Masahiko Kazuharu
Saito Aoki