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AssigneeResearch In Motion Limited
InventorsCurtis R. Leifso, Samuel A. Tiller
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A gain control circuit that permits a variable gain amplifier circuit to operate with high input linearity and low power consumption is disclosed. The variable gain amplifier includes a standard differential bipolar transistor input circuit and a pair of degeneration transistors connected to a current source transistor. The gain control circuit provides a variable degeneration control voltage to vary the effective resistance of the degeneration transistors and a variable bias voltage to vary the current of the current source transistor. The input linearity of the variable gain amplifier is controlled independently of gain by adjusting the effective resistance and the current in an inverse relationship such that at maximum gain the current is at a maximum while the degeneration resistance is at a minimum, and at minimum gain the current is at a minimum while the degeneration resistance is at a maximum. Therefore the variable gain amplifier can be controlled to operate with high input linearity and low power at lower ranges of gain.
An automatic gain control circuit for controlling input linearity of a variable amplifier in response to a control voltage, the control circuit comprising:
A degeneration control circuit for controlling degeneration transistors of a variable amplifier circuit in response to first and second bias control voltages, the degeneration control circuit comprising:
A method of controlling the gain of a variable amplifier, the variable amplifier having an amplifier coupled to a bias current source by a degeneration resistance, the method comprising the steps of:
A method of controlling the gain of a variable amplifier, the variable amplifier having an amplifier coupled to a bias current source by a degeneration resistance and also coupled to a known impedance, the method comprising the steps of:
Dependencies are inferred from the claim text.