Freescale introduces two final-stage LDMOS RF power transistors giving designers a choice between discrete and integrated circuit (IC) solutions. The transistors are optimized for use in power amplifiers based on Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). Freescale’s devices include the MRF7P20040H LDMOS FET and the MD7IC2050N multi-stage integrated power amplifier IC. The designer can select a discrete, three-stage PA configuration with the MRF7P20040H as the final amplifier, or the MD7IC2050N IC (which includes the driver and final amplifier stages) in a two-stage PA configuration.
Both devices are suited for use in Doherty amplifiers, which are universally employed in today’s base station transceivers. A Doherty amplifier consists of two amplifiers that operate under different transmit-signal conditions and typically require separate transistors for each amplifier. However, Freescale’s MRF7P20040H and MD7IC2050N support a dual-path configuration, which allows a Doherty amplifier to be constructed using a single device rather than two for the final-stage amplifier. In addition, since both devices are inherently broadband, they can operate in both bands allocated for TD-SCDMA (1880 to 1920 MHz and 2010 to 2025 MHz), so the same device can be used to provide RF power in both bands. Together, these advantages can significantly reduce a TD-SCDMA amplifier’s size, bill-of-materials and circuit complexity, while also simplifying inventory management.
Doherty amplifier reference designs
Freescale’s introduction of two Doherty amplifier reference designs can shorten the amplifier design cycle. The first employs Freescale’s MMG3014N general-purpose amplifier driving the MD7IC2050N to produce a two-stage IC-based lineup that delivers 35 percent efficiency at 10 W average RF output and a total gain of 45 dB. The second employs Freescale’s MMG3014N as the pre-driver, the MW6S004N LDMOS FET as the driver and the MRF7P20040H as the final amplifier stage. The result is a three-stage, discrete-based lineup that delivers 38 percent efficiency at 10 W average RF output and 50 dB of total gain.
Source: www.channel-e.biz