Amplifiers – Modulator-demodulator-type amplifier
Patent
1999-09-03
2000-12-05
Pascal, Robert
Amplifiers
Modulator-demodulator-type amplifier
330124R, H03F 338
Patent
active
061572535
ABSTRACT:
A radio frequency signal (FIG. 2, 205) is sampled and the sample is conveyed to a video detector (220). The detected envelope amplitude is sent to an envelope tracking circuit (280), a comparator (230), and an envelope tracking and gate biasing circuit (240). Based on the instantaneous value of the envelope amplitude, the comparator (230) selects one of the available supply voltages (340) via switch drivers (270). The selected one of the available supply voltages (340) is adjusted by the envelope tracking circuit (280) and the resulting voltage output (282) is supplied to the drains of the power amplifiers (390), thus enabling operation near saturation. As the instantaneous value of the envelope amplitude increases, the comparator (230) selects higher supply voltages (340) which increases the voltage conveyed to the power amplifiers (390), thereby increasing their power output. In order to maintain constant gain performance, the envelope tracking and gate biasing circuit (240) modifies the gate bias inversely with the changes the drain voltage.
REFERENCES:
patent: 4831334 (1989-05-01), Hudspeth et al.
patent: 5757229 (1998-05-01), Mitzlaff
patent: 5886572 (1999-03-01), Myers et al.
patent: 5936464 (1999-08-01), Grondahl
patent: 5942938 (1999-08-01), Myers et al.
patent: 6064269 (1999-08-01), Ruppel et al.
Myers Ronald Gene
Sigmon Bernard Eugene
Bogacz Frank J.
Choe Henry
Limon Jeff D.
Motorola Inc.
Pascal Robert
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