BROADBAND POWER of 100 W or more usually implies vacuum-electronics circuitry surrounding one or more traveling-wave tubes. But the model 8767 broadband Amplifier Technology Ltd. is a 100-W power amplifier designed for applications from 500 to 2500 MHz, and based on solid-state gallium-nitride (GaN) transistors. It extracts all that output power from a package that is only 261 x 131 x 31 mm with SMA input and output connectors.

Model 8767 makes use of semiconductor devices which are fabricated on III-V wide-bandgap semiconductor material. The compound semiconductor material has been used by a number of device manufacturers for wireless applications, and is starting to make its way into compact amplifiers for pulsed and continuous-wave (CW) applications in communications, radar, and electronic-warfare (EW) systems. The wide-bandgap nature of GaN makes is well suited for high-power, high-frequency applications. It has been used for some time in light-emitting diodes (LEDs), including blue and violet types, but also more recently in high-power RF/microwave transistors, including metal-oxide-semiconductor-field-effect-transistor (MOSFET) and high-electron-mobility-transistor (HEMT) devices.

The epitaxial material has high heat capacity and high thermal conductivity. It also has high mechanical stability and resists cracking, making it suitable for deposition on silicon carbide substrates for extremely high power devices with good thermal properties. The high breakdown voltage, high electron mobility, and high saturation velocity of GaN make it ideal for RF and microwave power amplifiers, such as the model 8767.

This model (Fig. 1) is manufactured as a commercial-off-the-shelf (COTS) product suitable for commercial, industrial, military, and medical applications. It is supplied in a coaxial housing small enough to fit into most radar and jamming applications. It achieves the rated output power when fed with an input signal at +0 dBm, operating with 30 percent power-added efficiency.

In terms of power for its size, the model 8767 from Amplifier Technology Ltd. compares favorably with another broadband GaN power amplifier, the model 1179- BBM3K5KKO from Empower RF Systems. The model 1179 measures 7.874 x 4.134 x 1.06 in. (200 x 103 x 26.92 mm) with SMA female input and output connectors, and is rated for 125 W typical saturated output power and 50-dB minimum gain at 50 W typical 1-dB output power from 500 to 2500 MHz. It consumes 15 A maximum current from a +28 VDC typical supply.

The rugged model 8767 GaN power amplifier maintains flat gain within a 1-dB window across its wide operating bandwidth (Fig. 2). It consumes maximum current of 15 A from a voltage supply of +28 2 VDC. Harmonic levels are typically -20 dBc at the rated output power level. Model 8767 power amplifiers are assembled in an ISO 9001:2000 facility utilizing Six Sigma and Lean manufacturing practices.

AMPLIFIER TECHNOLOGY LTD., Unit 5, Easter Court, Woodward Avenue, Westerleigh Business Park, Yate, Bristol, BS37 5YS, United Kingdom; +44 (0) 8700 869 941, FAX +44 (0) 8700 509 249, sales@amplifiertechnology.com, www.amplifiertechnology.com.