Four-Band Power Amp Eyes GSM/GPRS Cell Phones

The MMM6035 50-Ω power amplifier is destined for dual-, tri-, and quad-band GSM/GPRS cell phones (see the figure). This tiny two-chip module comprises a dual-amplifier die and a CMOS power-control die. Such a combination simplifies transceiver design requirements and eliminates the need for directional couplers and detector diodes.

Crafted by Freescale Semiconductor (formerly Motorola SPS), the RF chip is made with enhancement-mode gallium arsenide. It offers two separate RF amplifier chains, one for 850 and 900 MHz and the other for 1800 and 1900 MHz. The amplifers run class AB and feature fully integrated matching circuits for the internal stages as well as on the inputs and outputs.

The amplifier is GPRS class 12 compatible (up to 50% duty cycle). Efficiency runs 53% on the low bands and 45% on the high bands. The input power range is 3 dBm for both bands. The CMOS power-control chip, which ensures ripple over the entire frequency range, has a valuable antisaturation feature. It provides a 45-dB dynamic range with an analog input voltage.

The MMM6035 comes in a tiny 6- by 6- by 1-mm package. It's available now for $2.50 in 10,000-unit quantities.

See associated figure