RF power LDMOS amps boost efficiency in industrial radios

July 17, 2015 // By Graham Prophet
Freescale Semiconductor has added two broadband RF power amplifiers - the Airfast AFIC901N LDMOS RF integrated device and the AFT05MS003N LDMOS transistor. The products can be operated at 3.6 or 7.5V and are targeted for applications where power for radio range, and efficiency for battery life, are key design requirements.

Transition from analogue to digital modulation schemes usually requires a radio redesign. The efficiency these devices, says Freescale, allows land mobile radio OEMs to take advantage of the new transistors’ performance to enhance battery life. High gain provides an opportunity to reduce the number of transistors used, thus minimising system cost.

The Airfast AFIC901N LDMOS RF integrated device and AFT05MS003N LDMOS transistor have broad bandwidths that cover frequency bands between 136 and 941 MHz. They also offer high efficiency and gain, and are housed in compact and lightweight over-moulded plastic packages. Their extreme ruggedness (> 65:1 VSWR) enables highly robust handheld radios.

The transistors are suited for use in combination with Freescale microcontrollers for applications such as automatic meter readers that operate at 169, 434 or 868 MHz, where they can cost-effectively increase the application’s communication range. They are also suitable for other machine-to-machine applications and supervisory control and data acquisition (SCADA) systems.

The AFIC901N two-stage LDMOS device delivers 1W CW of RF output power with 63% efficiency and 30 dB gain at VHF frequencies between 136 and 174 MHz. The device is housed in a QFN 4 × 4 package. As it delivers its full 30 dBm rated power with an input power of 0 dBm, it eliminates the need for pre-amplification. The AFIC901N offers RF matching flexibility externally to the device at the input and output, as well as at the interstage level. This lets designers optimise the device for their particular system requirements, including multiple radio bands, by changing only a few discrete components on the circuit board.

The single-stage AFT05MS003N provides 3W of CW power. It covers 136 to 941 MHz with 17 dB gain and 67% efficiency in the VHF band. The AFT05MS003N is housed in a SOT-89 over-moulded plastic package. The new transistors join Freescale’s Airfast portfolio of 7.5 to 12.5 VDC transistors for mobile and M2M radio applications ranging from 1 to 75W.