Amplifier specifiers involved with selecting products for GSM cellular-telephone designs have learned to choose from a substantial list of module solutions. These modules are accompanied by one or two amplifier chips and a power-control IC, and sometimes still require external circuitry for DC blocking and impedance matching. In contrast, the Si4300 GSM/GPRS power amplifier (PA) from fabless-semiconductor company Silicon Laboratories (Austin, TX) is a complete monolithic amplifier integrated circuit (IC), a single device that includes all the functions between a GSM handset transceiver and the antenna/switch module. Operating in both the GSM 900 (880-to-915-MHz) and DCS 1800 (1710-to-1785-MHz) bands, the IC includes the amplifiers, harmonic filtering, complete power-control circuitry, and impedance matching and requires no external discrete components.
Unlike most (GaAs) GSM handset PAs, the Si4300 (see figure) is made with a standard 0.35-µm silicon CMOS process. By using a novel circuit design employing distributed device stages, the Si4300 can achieve the high voltages needed for high-gain amplification in CMOS. Unlike GaAs-based PA modules which can measure 7 × 10 mm or more, the Si4300 is supplied as a single die in a compact 3.9 × 6.4 mm ceramic package. Like the GaAs PA modules, the Si4300 is designed for voltages from +3.0 to +5.5 VDC.
The Si4300 features a GSM output-power level of +34.7 dBm and DCS output-power level of +32.3 dBm, while achieving typical power-added efficiency of better than 50+ percent. Silicon Laboratories, Inc., 4635 Boston Lane, Austin, TX 78735; (512) 416-8500, (877) 444-3032, FAX: (512) 464-9444, e-mail: PAinfo@silabs.com, Internet: www.silabs.com.