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GaAs MMICs enable signal pre-amplification

Posted: 05 Jul 2010 ?? ?Print Version ?Bookmark and Share

Keywords:GaAs base station? MMIC? power amplifier? LNA?

Freescale Semiconductor is building on its business in lateral-diffusion MOS discrete power transistors for base station apps to enter integrated GaAs RF chip market. The ultralow-noise GaAs chips promise enable pre-amplification of radio signals without also magnifying noise.

The first members of Freescale's GaAs monolithic microwave IC (MMIC) family are LNAs and power amplifiers (PAs) for wireless base stations, repeaters and femtocells.

"Our LDMOS devices are already used in seven out of 10 base stations, and our new MMICs likewise meet the need for extremely low-noise amplification and supply low current in wireless infrastructure equipment, including new application areas in avionics, broadcast and ISM," said Freescale marketing manager Jeannette Wilson. "The devices are optimized for the high gain and low power consumption critical for long-term reliability."

The four GaAs parts are the first in what Freescale promises will be a growing family based on its patented indium gallium phosphide (InGaP) heterojunction bipolar transistors, heterojunction FETs and enhancement-mode pseudomorphic high-electron-mobility transistors (pHEMTs). Designed for both general-purpose and low-noise power amplification, the devices target 3G and 4G base station applications.

The enhancement-mode pHEMT MMICs have a low noise figure of less than 0.6dB (including circuit losses), provide a small-signal gain of more 20dB at 900MHz and operate in any band from 400MHz to 1,400MHz, according to Freescale.

The family also includes a two-stage InGaP HBT power amplifier for the 1,800MHz to 2,200MHz band used by base stations, repeaters and femtocells. The two other initial family members function as driver- and second-stage LNAs in the 500MHz to 2,800MHz and 1500MHz to 2400MHz bands, respectively.

Freescale has also extended its LDMOS power FET family with ultra-rugged 50V models that are designed to prevent catastrophic reflection of standing waves during startup while continuing to transmit at 300W, with a 65:1V standing wave ratio.

The FETs were designed for conventional applications in carbon dioxide lasers, magnetic resonance imaging and plasma generators for semiconductors and solar cell coatings, but their higher-voltage operation has also won them applications in FM broadcast transmitters, mobile radios, radar, solid-state synchrotrons and RF-illumination lighting.

- R. Colin Johnson
EE Times

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