Dynamic bias control in power amplifier

Telecommunications – Transmitter – Power control – power supply – or bias voltage supply

Reexamination Certificate

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C455S552100, C330S136000

Reexamination Certificate

active

07729672

ABSTRACT:
An RF output power amplifier (PA) of a cellular telephone includes first and second Class AB amplifier circuits. If the cellular telephone is to operate in a high power operating mode, then the first amplifier drives the PA output terminal. The power transistor(s) in the first amplifier is/are biased at a first DC current and a first DC voltage so as to optimize efficiency and linearity at high output powers. If the cellular telephone is to operate in a low power operating mode, then the second amplifier drives the output terminal. The power transistor(s) in the second amplifier is/are biased at a second DC current and a second DC voltage so as to optimize efficiency and linearity at low output powers. By sizing the power transistors in the amplifiers appropriately, emitter current densities are maintained substantially equal so that PA power gain is the same in the two operating modes.

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patent: 6606483 (2003-08-01), Baker et al.
patent: 6804500 (2004-10-01), Yamaguchi
patent: 6882194 (2005-04-01), Belot et al.
patent: 7474880 (2009-01-01), Pan
patent: 2007/0080750 (2007-04-01), Liebenrood
International Search Report—PCT/US07/064724—International Search Authority—European Patent Office—Nov. 30, 2007.
Chul Soon Park et al: “An InGaP-GaAs HBT MMIC smart power amplifier for W-CDMA mobile handsets” IEEE Journal of Solid State Circuits, IEEE Service Center, Piscataway, NJ, USA vol. 38, No. 6, Jun. 2003 pp. 905-910, XP011097039.
Written Opinion—PCT/US07/064724—International Search Authority—European Patent Office—Nov. 30, 2007.

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