Patent ID: 6693492
Filing Date: 2004-02-17
Classification: H03F,H03G

Abstract:
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 an 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; and an impedance correcting circuit connected across said input circuit for reducing input impedance of the input signal in accordance with increasing input impedance of said amplifying transistor comprising a variable conductive device having a control electrode coupled to receive the gain control voltage.