Date: 26/04/2011

LDMOS RF power transistors supporting PCS and TD-SCDMA standards

Freescale Semiconductor has introduced two LDMOS RF power transistors that allow wireless base station amplifiers to cover all channels in an entire allocated frequency band. Freescale says its new RF power LDMOS transistors deliver a compelling combination of high linearity, high efficiency, wide instantaneous bandwidth and high power that extend the instantaneous signal bandwidth to an industry-leading 160 MHz, making them ideal for these next-generation amplifier systems.

Freescale's MRF8P20165WH/S for the 1930 to 1995 MHz PCS band and the MRF8P20140WH/S for the 1880 to 2025 MHz TD-SCDMA bands F & A, can support the corresponding wireless spectrum with one amplifier. Since wideband/multi-band PAs are generally agnostic to modulation formats, operators can upgrade to 4G LTE and other wireless standards with only a software change and no additional hardware.

"The need for RF power transistors to deliver exceptional linearity and efficiency over a full wireless band is no longer simply desirable; it is essential," said Ritu Favre, vice president and general manager of Freescale's RF Division. "The devices we are introducing today are the first in a family of broadband RF power transistors that includes all current and emerging wireless bands. Each device will be designed to combine all of the attributes - high efficiency and linearity and high output power- required to allow carriers to meet the challenges of the future."

Freescale's MRF8P20165WH/S and MRF8P20140WH/S meet linearity requirements for PCS and TD-SCDMA standards while delivering efficiency of at least 43.7 percent when amplifying multiple wireless carriers separated by up to 65 MHz (PCS) and 10 MHz (TD-SCDMA). Both devices are dual-path designs, and can implement the final stage of a Doherty amplifier with one path as the main amplifier and the other as the peaking amplifier.

Key specifications of the new RF power LDMOS devices:

MRF8P20165WH/S (1930 to 1995 MHz)
37 W average power with input signal peak-to-average ratio (PAR) of 9.9 dB
47.7% drain efficiency
16.3 dB typical power gain

MRF8P20140WH/S (1880 to 2025 MHz)
24 W average power with input signal PAR of 9.9 dB
43.7% drain efficiency
16 dB typical power gain

Both devices are designed for use in Doherty amplifier configurations and digital pre-distortion. These rugged devices can handle a 10:1 VSWR impedance mismatch when operating at 32V and driven with twice their recommended input power. The transistors are internally matched with low capacitance to simplify circuit design and have integrated electrostatic discharge (ESD) protection. Their gate-source voltage range of -6 to +10V increases their performance when operated in Class C mode. The transistors are housed in Freescale's NI-780-4 and NI-780S-4 air cavity packages.


Pricing and availability: The MRF8P20165WH/S and MRF8P20140WH/S are available in sample quantities, and full production is expected in May 2011. A reference design and other support tools are available to designers.