Variable reactance circuit including differentially-connected transistor device providing a variable reactance input impedance
AssigneeSony Corporation
InventorsMasayuki Hongu, Masahiro Tada
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Abstract
A variable reactance circuit is composed of a differential amplifier having first and second emitter-coupled transistors, a reactance element, such as a capacitor, connected between the collector and base electrodes of the first transistor, and a control signal source connected to the emitter electrodes of the transistors by which the input impedance of the first transistor is effective as a variable reactance which is changed in accordance with the level of the control signal. Such variable reactance circuit may be used with an oscillator or resonance circuit to constitute a frequency modulator controlled by the control signal source.
Claims10
A variable reactance circuit comprising first and second transistors each having base, emitter and collector electrodes, said emitter electrodes of said first and second transistors being connected together, a a reactance element connected between said base electrode and said collector electrode of said first transistor, bias circuit means for applying a predetermined DC voltage to said base electrode of at least said second transistor, and a control signal source for applying a control signal to said connected together emitter electrodes of said first and second transistors so that the input impedance of said first transistor, as viewed from its base electrode, constitutes a variable reactance which varies in accordance with the level of said control signal.
Dependencies are inferred from the claim text.