R.F. amplifier circuit
AssigneeHitachi, Ltd.
InventorHiroshi Kimura
Life of this patent
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Abstract
An R.F. amplifier circuit having a high selectivity with a simple and inexpensive construction is provided. An R.F. choke coil acting as a bias supplying element is connected to a collector of an amplifying transistor to supply it with an optimum biasing current for a high electric field strength. A first capacitor is connected in parallel, at a high frequency, with the R.F. choke coil, which is connected to an LC tuning circuit through a second capacitor. A resonance frequency of the R.F. choke coil and the first capacitor is chosen to be sufficiently lower than that of the LC tuning circuit to maintain a single tuned circuit while at the same time an output impedance of the amplifying transistor is stepped up by the first and second capacitors to insure a high quality factor.
Claims2
An R.F. amplifier circuit having an LC parallel tuning circuit at an output thereof comprising;
- an R.F. choke coil connected between an output electrode of an amplifying transistor and a power supply and having a sufficiently low D.C. resistance,
- a first capacitor connected between said output electrode and a ground across said amplifying transistor, and
- a second capacitor connected between said output electrode and said LC parallel tuning circuit,
- a resonance frequency of said first capacitor and said coil being selected to be sufficiently lower than a resonance frequency of said tuning circuit.
An R.F. amplifier circuit comprising;
- an R.F. amplifying transistor for amplifying an R.F. input signal applied to a base thereof,
- a driving power supply for said transistor,
- an R.F. choke coil connected between a collector of said transistor and said power supply for supplying a collector bias current therethrough to said transistor,
- a first capacitor connected between the collector and an emitter of said transistor,
- a parallel resonance circuit including parallel connected inductor and capacitor, at least one of inductance and capacitance thereof being variable, and
- means including a second capacitor for connecting said parallel resonance circuit across the collector and the emitter of said transistor through said second capacitor.
Dependencies are inferred from the claim text.