Variable gain low-noise amplifier and method
AssigneeInternational Business Machines Corporation
InventorPaul B. Desize
Life of this patent
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Abstract
A degenerating device is connected between the emitter of the amplifying transistor and ground. A resistor connected across the FET switch provides a finite limit, the total resistance in the emitter circuit of the amplifying transistor. Additional circuitry may be provided in the emitter-based circuit of the amplifying transistor such as an impedance correcting circuit designed to compensate for changing base input impedance, the result of change in the resistance of the degeneration circuit.
Claims14
A variable gain low-noise amplifier comprising:
- a common emitter amplifying transistor for receiving an input signal to an input circuit at the base of said amplifying transistor at an input frequency and providing an output signal at its collector;
- a degenerative circuit connected in the emitter-ground circuit of said amplifying transistor, said degenerative circuit comprising a transistor conductive circuit and a resistor connected thereacross;
- a control electrode for coupling to a source of bias voltage, said resistor providing for a maximum resistance of said degenerative circuit, said control electrode also being coupled for receiving a gain control voltage for varying resistance of said conductive circuit in accordance with the gain control voltage.
A method for degenerative control gain in a variable low-noise common emitter amplifier comprising the steps of:
- increasing resistance of an emitter ground circuit of said amplifier in accordance with a gain control signal to provide degenerative operation;
- and
- limiting increase in the resistance to a maximum amount.
Dependencies are inferred from the claim text.