NEC Corp. announced its development of a compact gallium nitride (GaN) power transistor amplifier, which the company claims has the world's highest output power level of 400W with low-distortion characteristics. The amplifier is composed of a single transistor package under a W-CDMA scheme, without using any power-combining circuits.
Specifically, the GaN power transistor was designed to achieve high output power density under high-current (1A/mm) and high voltage (45V) operation owing to NEC's proprietary field-modulating plate technology, which reduces the electric field strength at the gate edge, leading to improved breakdown voltage, and enables high-voltage, high-power operation. The single-ended GaN power amplifier also contains a compact configuration decreases the number of assembled RF components and a newly-developed output bias networks inside the amplifier suppress the memory effect of the amplifier, thereby achieving excellent linearity with a digital predistorter placed within.
The need to achieve a large-capacity and high-speed system is becoming more crucial with the rapid increase in traffic accompanying the swelling number of 3G mobile subscribers and increasingly sophisticated and diversified 3G services worldwide. To achieve such a system a power amplifier with higher output power and high linearity for 3G base stations is vital. To achieve this, the amplifier also needs to realize energy savings and compact size.
Conventional amplifiers composed of silicon LDMOS transistors or gallium arsenide (GaAs) transistors require power-combining circuits due to the small output power of each transistor. As a result, the amplifier is larger in size and there is an increased loss in power. These factors make it difficult to achieve a high output power amplifier with compact size and high efficiency.
