Transistor developers continue to push for higher power levels from a single die or package, but not to the exclusion of other performance parameters. Especially for commercial communications applications, device designers now emphasize improved linearity and efficiency so that amplifier designers can create smaller and lighter units for mobile radios and compact base stations. What follows is a sampling of recent developments in RF and microwave power transistors.
Several device announcements were made at the recent IEEE Microwave Theory & Techniques Symposium (MTT-S, June 10-12, Philadelphia, PA), including the launch of several high-voltage high-frequency (HF) MOSFET devices by Advanced Power Technology RF (www.advancedpower.com). Both are nominally intended for HF amplifiers and RF plasma generators at frequencies from 1.5 to 30 MHz. The ARF465A/B, for example, dissipates as much as 250 W power and generates as much as 125 W output power when operating with a +300-VDC supply. The larger model ARF1505 dissipates as much as 1500 W power and generates output levels to 750 W CW from a +300-VDC supply. The rugged design features a power density of 700 W/in.2
At the show, the company also announced two new lateral-diffused MOS (LDMOS) transistors for pulsed avionics and radar applications, the 110-W peak-power model 1011LD110 and the 200-W peak-power model 1011LD200. The +32-VDC transistors offer gain levels of 13 and 12 dB, respectively, over the 1030-to-1090-MHz Identify Friend or Foe (IFF) avionics band.
Advanced Semiconductor (www.advancedsemiconductor.com) features a wide range of CW and pulsed RF power transistors, including a wide range for DME/TACAN avionics applications from 1025 to 1150 MHz. Several devices with internal input and output matching networks offer output-power levels of 250 W and more, including the 400-W model AVD400 and the 500-W model AVD500. These +50-VDC parts both feature minimum efficiency of 40 percent with respective gains of 6.5 and 5.6 dB.
Philips Semiconductors (www.semiconductors.philips.com) is a long-time supplier of high-power transistors, and features several RF bipolar models for TACAN and JTIDS avionics applications (roughly 960 to 1215 MHz), including the models MX0912B251Y and the MX0912B351Y. The former features 275 W of pulsed output power while the latter produces 375 W of pulsed output power. Both devices yield 7.5-dB gain at 45-percent efficiency.
Another veteran device supplier, M/A-COM (Tyco Electronics), offers both power bipolar and MOSFET devices for a wide range of applications, including the model PH1090-700B bipolar transistor for pulsed avionics applications. The gold-metalized, ceramic-packaged device delivers 700 W of pulsed (32-µs pulses at a 2-percent duty cycle) output power from 1030 to 1090 MHz. The +65-VDC device features 7.5-dB power gain with 50-percent collector efficiency.
Additional high-power silicon transistor suppliers include Polyfet RF Devices (www.polyfet.com) and Point Nine Technologies (www.pointnine.com). Polyfet's model SR401 is a +28-VDC push-pull transistor capable of 300 W output power at 175 MHz. The transistor features 13 dB gain and 55-percent efficiency.
Point Nine's model C203, one of the company's line of TetraFET devices, is usable to 1 GHz. The silicon DMOS device employs gold metalization to gain 100 W output power from a +28-VDC supply. The rugged transistor achieves 10 dB gain with 40-percent drain efficiency. Another of the company's TetraFETs, the model D1027, provides 200 W output power at frequencies from DC to 300 MHz. The +28-VDC transistor generates 17 dB gain with 50-percent efficiency.
"Plastic" was the key word at the Motorola (www.motorola.com) booth during the show, as the company unveiled several plastic-packaged MOSFETs, including the MRF5S9101MR1 which is designed for applications to 1 GHz. The device yields 105 W 1-dB-compression CW output power at 960 MHz with 16.5 dB gain and 56-percent efficiency. Capable of operating at +26 or +28 VDC, the device is well suited for GSM base-station applications, with error-vector-magnitude (EVM) performance of 3 percent.
STMicroelectronics (www.us.st.com) is developing a new family of +100-VDC high-power VHF/UHF MOSFETs. The new process utilizes enhanced raised-gate technology for feedback capacitance reduction and optimized deep body doping to improve load mismatch tolerance. Proprietary techniques result in increased breakdown voltages and reduced parasitic capacitance, with a 6-dB increase in power gain compared to standard +50-VDC devices. The transistors employ thermally enhanced nonpedestal packaging and will be available in 150-W (model SD3931-10) and 300-W (model SD3933) single-ended configurations as well as a dual 300-W (model SD3932) configuration. The devices are currently being evaluated in a variety of applications, including plasma generators and magnetic-resonance-imaging (MRI) systems.
At somewhat higher frequencies, Mitsubishi Semiconductors (www.mitsubishichips.com) announced the availability of a pair of internally matched GaAs FET devices for Ku-band very-small-aperture-terminal (VSAT) satellite-communications applications. The model MGFK41A4045 delivers 12 W output power in the 14.0-to-4.5-GHz VSAT band while the model MGFK44A4045 produces 24 W output power from 14.0 to 14.5 GHz.
Also serving satellite-communications applications, the TIM5964-90SL GaAs FET from Toshiba America Electronic Components (www.taec.toshiba.com) promises 90 W (+49.5 dBm) output power from 5.9 to 6.4 GHz. The internally matched C-band transistor helps amplifier designers reduce the number of parts in their designs by replacing several lower-power devices. The transistor features 7 dB typical gain with 30-percent typical power-added efficiency (PAE) and a third-order intermodulation distortion (IMD) of typically −40 dBc.
The use of internal impedance matching allows Excelics Semiconductor (www.excelics.com) to provide as much as 8 W output power at VSAT frequencies. For example, the company's models EIA1415A-8P and EIA1415B-8P are internally matched GaAs FETs with 6 and 8 dB gain, respectively, from 14.0 to 15.35 GHz; both devices yield 8 W output power over that range. The devices are rated for PAE of 20 percent and third-order intercept point of +46 dBm.
Another supplier with an extensive lineup of internally matched devices, Fujitsu Compound Semiconductor (wwwfcsi.fujitsu.com), offers numerous C-band devices include the model FLM3742-25F. Designed for +10-VDC supplies, the transistor achieves +44.5-dBm output power with 10.5 dB typical gain and 41-percent efficiency from 3.7 to 4.2 GHz.
California Eastern Laboratories (www.cel.com) offers the NE650103M power GaAs FET for L- and S-band applications through 2.7 GHz. Ideal for PCS and wireless-local-loop (WLL) applications, the device operates from a +10-VDC supply with 10 W (+40 dBm) output power and 42-percent typical efficiency. The power gain is typically 11 dB at 2.7 GHz.
Several power-transistor processes that have yet to gain wide acceptance among amplifier designers include those based on silicon-carbide (SiC) and gallium-nitride (GaN) substrates. For the former, Cree (www.cree.com) has offered several versions of a 10-W device for several years. Now available as model CRF-24010, the device is usable to 2.7 GHz with at least 10 W output power and 15 dB gain.
Because of the high-power potential of materials such as SiC and GaN, large defense contractors such as BAE Systems (www.baesystems.com) and Northrop Grumman Corp. (www.northgrum.com) have made major investments in device development. More details will be available at the upcoming Third Annual Military Electronics Show (www.mes2003.com, Baltimore, MD, September 16-17, 2003).