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29 January 2009


Cree samples GaN HEMT microwave transistors for telecom applications

Cree Inc of Durham, NC, USA has announced the sample release of two 120W, highly efficient gallium nitride HEMT microwave transistors for telecoms applications such as W-CDMA, LTE and WiMAX.

The firm claims that, due to a unique combination of high RF power density, low capacitance and high-thermal-conductivity silicon carbide (SiC) substrates, the transistors provide superior performance compared to other technologies such as GaAs MESFET or silicon LDMOSFET. Two demonstration amplifiers—one for each device—are available for transistor evaluation.

The new transistors consist of single, input-pre-matched GaN HEMT devices providing more than 120W of saturated power in small, industry-standard ceramic-metal packages. The transistors provide what is said to be convenient values of input and output impedances to allow device matching over greater than 30% instantaneous bandwidths.

The CGH21120F is designed to be used primarily in the 1800-2300MHz frequency range, while the CGH25120F is optimized for the 2300-2700MHz range, allowing use for DCS (GSM), PCS (GSM and CDMA), W-CDMA, and LTE.

As an example, the CGH21120F provides more than 110W of peak CW power at 70% efficiency with a gain of 16dB when operated at 28V. Under W-CDMA 3GPP stimulus, the transistor provides 25W average power with 40% efficiency in Class A/B operation. This is claimed to be the highest known W-CDMA efficiency from any commercially available transistor at this power level.

Each transistor has demonstrated the performance needed for demanding 3G and 4G telecom networks, says Jim Milligan, director of RF and microwave products. “High efficiency is becoming a driving factor, along with increased emphasis on higher average powers, for multi-channel/carrier applications,” he adds. “These transistors also allow a high degree of digital pre-distortion correction, so that ACLRs (adjacent channel level ratios) of -60dBc can be routinely achieved.” In a recent demonstration, two CGH21120F transistors, in a Doherty amplifier configuration, generated 80W of average power under W-CDMA with a record efficiency of 52%.

The CGH21120F and CGH25120F complement the range of Cree’s RoHS-compliant HEMT microwave transistors for WiMAX applications available for 802.11x OFDM average power levels of 2, 4 and 8W.

See related items:

Digi-Key expands Cree portfolio to GaN HEMTs

Cree samples high-efficiency 120W GaN HEMT microwave transistor

Search: Cree GaN HEMT WCDMA LTE WiMAX SiC substrates


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