High-Power Transistors Focus On Emerging Applications

Todays high-power transistors push emerging applications ahead while research and development finds ways to give these transistors even more muscle.

Transistors may seem like simple devices. The reality, however, is that an impressive lineage of research and development stands behind each transistor. Often, the companies that make these devices have spent years on their technologies and approaches. They come out the other end as specialists in their transistor domain—be it silicon-carbide (SiC), LDMOS, or one of the many other technical variations. For instance, the MOSFET expertise of Integra Technologies, Inc. (El Segundo, CA) has allowed the company to achieve an industry first in the IMOS transistors. These transistors claim to be more rugged while offering a higher power density than LDMOS offerings, making them suitable for the avionics industry.

Many companies are now bending their expertise in high-power transistors to target the burgeoning broadband market. For example, Cree, Inc. (Durham, NC) recently began shipping its 10-W packaged SiC MESFET. Dubbed the CRF35010, it is optimized for broadband-wireless-access (BWA) and Wireless Interoperability for Microwave Access (WiMAX) applications. When operated at 48 V, the CRF35010 typically produces 1.5 W of average output power and 17 percent drain efficiency with 10-dB small signal gain with orthogonal-frequency-division-multiplexing (OFDM) modulation.

Another company that is homing in on the broadband arena is Polyfet RF Devices (Camarillo, CA). Its expansive broadband product portfolio includes MOSFET, MOSFET LDMOS, and MOSFET VDMOS transistors. In addition, Toshiba America Electronic Components, Inc. (Irvine, CA) has five new high-gain, high-linearity, internally matched GaAs field-effect transistors (FETs). These FETs target amplifiers and microwave digital radios for 3.5-GHz and 5-GHz fixed-wireless-access (FWA) systems including WiMAX and Unlicensed National Information Infrastructure (U-NII)-compatible systems. For fixed-wireless-system applications that demand maximum output-power levels, TAEC has added two devices to its Super Linear (SL) device family. The 16-W TIM3438-16SL flaunts 12.5-dB gain and typical output power of +42.5 dBm. Its sibling, the 60-W TIM5359-60SL, offers 9.0 dB gain and a typical output power of +48.0 dBm.

TAEC also extended its Ultra-Linear (UL) GaAs FET product line by adding devices in the new 5.3 to 5.9-GHz frequency range. The TIM5359-4UL achieves high gain of 10.5 dB with a typical output power of +36.5 dBm. The TIM5359-8UL provides 10.0 dB gain and typical output power of +39.5 dBm while the TIM5359-16UL offers the same gain with +42.5 dBm typical output power.

In a separate announcement, Toshiba is targeting the satellite-communications (SATCOM) arena (see figure). Its two new internally matched, Ku-Band-power, gallium-arsenide field-effect transistors (GaAs FETs) promise to provide increased linearity and higher output power for SATCOM applications. At a frequency range of 14.0 to 14.5 GHz, the 9-W TIM1414-9L features high power output of +39.5 dBm. The 30-W TIM1414-30L boasts an impressive power output of +45.0 dBm (typ.) at a frequency range of 14.0 to 14.5 GHz. These GaAs FETs are implemented in Toshiba's Heterojunction Field Effect Transition (HFET) process technology, which is said to enhance both output power and gain.

The telecommunications arena also is a hot area for high-power transistors. Two recent breakthroughs come from Infineon Technologies (Morgan Hill, CA) and Philips Semiconductors (Eindhoven, The Netherlands). Infineon's GM8/GM9 technologies are well suited for WCDMA, CDMA, and GSM/EDGE applications. For two-carrier CDMA applications, the preliminary GM9 150-W singled-ended device vows to provide 27 W of CDMA power at 27 percent drain efficiency at –37 dBc IMD. It promises to provide more than 29 percent efficiency at 34-W average power for WCDMA applications at –37 dBc. The company also released its preliminary GM8IC products, which include the 45-W WCDMA/CDMA/TDCDMA IC with 25 dB gain, a 400-MHz-wide bandwidth, and 50-W P1dB under CW condition. Two 20-W products add to the mix. The 0.9-GHz GSM/EDGE/CDMA IC offers 35 dB gain. It claims to meet all GSM/EDGE EVM and ACPR specifications as well as the CDMA ACPR specifications. Those same specifications also are met by a 1.9-GHz IC with 30-dB gain.

The latest products from Philips comprise its fifth-generation LDMOS for base-station RF power amplifiers (PAs). The LDMOS technology suits all base-station PA frequency bands from 800 MHz to 2.2 GHz. The output power of a final-stage transistor can be over 160 W. With the fifth-generation technology, the final stage gain is supposedly increased by 5 dB. For two-carrier WCDMA that is 10 MHz apart at a PAR of 8.5 dB at 0.01 percent probability on CCDF, the average output power for the BLC5G22LS-100 is 26 W. Its peak power is 165 W (pulsed CW). The frequency range is 2000 to 2200 MHz. The device boasts a gain of 18.5 dB, a supply voltage of 28 V, IMD of –36 dBc, and 30 percent efficiency. The new product family consists of four products for the 2.2-GHz UMTS band, three products for the 2.0-GHz GSM/PCD/DCS/CDMA bands, and two products for the 800 to 1000-MHz GSM/CDMA bands.

These recent product breakthroughs are just a small sampling of the extensive and ongoing developments in the high-power-transistor arena. Such developments will only increase as companies investigate new paths toward reaching even higher power output. For example, Toshiba is currently researching the use of gallium-nitride (GaN). It plans to use GaN to develop 50-W and 100-W class devices in the Ku-Band. Cree also happens to be doing research and development on GaN. Clearly, gallium-nitride could hold the performance key to future applications. No matter its fate, however, progress is sure to continue in all areas of the high-power-transistor market.

By offering either high output power or power efficiency, these GaAs FETs can target the high-power SSPAs used in earth or base stations or the block-upconverter modules in Ku-Band transceivers.

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