Television tuning circuit utilizing voltage variable capacitance

Claim 1

In a VHF television tuner wherein VHF television signals are heterodyned in a mixer stage with locally generated signals from an oscillator stage to produce an intermediate frequency signal, an electric circuit comprising: an input and an output tunable resonant circuit adapted to maintain a bandwidth of at least 6 MHz. at all its tunable frequencies, each tunable resonant circuit including a first and a second inductor connected in series and a variable capacitor and a third inductor connected to form a resonant circuit, said resonant circuit coupled between the junction of said first and said second inductor and a point of reference potential; a first transistor having a base electrode, a collector electrode and an emitter electrode and connected to form a grounded base amplifier; said input tunable resonant circuit first and second inductors coupled between a source of VHF television signals and the emitter electrode of said first transistor; a second transistor having a base, a collector and an emitter electrode; a wideband tuned circuit interconnecting the collector electrode of said first transistor and the base electrode of said second transistor; and said output tunable resonant circuit first inductor and second inductor coupled between one of said second transistor collector and emitter electrodes and said mixer stage.