Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2005-03-22
2005-03-22
Nguyen, Khanh V. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S278000, C330S283000
Reexamination Certificate
active
06870425
ABSTRACT:
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.
REFERENCES:
patent: 4866314 (1989-09-01), Traa
patent: 6163215 (2000-12-01), Shibata et al.
patent: 6674327 (2004-01-01), Harberts
patent: 6684065 (2004-01-01), Bult et al.
Leifso Curtis R.
Tiller Samuel A.
Jones Day
Liang Robert C.
Nguyen Khanh V.
Pathiyal Krishna K.
Research in Motion Limited
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