A multiband power amplifier using combination of CMOS and GaAs technologies for WCDMA handsets

A multiband power amplifier using combination of CMOS and GaAs technologies (Combo MB PA) which supports quad WCDMA bands (Band V, VIII, II, I) is described. With four chips - two GaAs-HBT chips, a GaAs-HEMT chip, and a CMOS chip - mounted on a 5.5×5mm
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laminate, the Combo MB PA comprises two amplifier chains and two SPDT HEMT band-select switches, covering 824-915MHz and 1850-1980MHz. Each amplifier chain has switchable signal paths corresponding to dual (high and low) power modes (HPM and LPM) for saving battery current in practical handset use. In the PA, driver stages, RF switches, and their bias- and switch-control circuits are integrated on the CMOS chip for cost reduction. Only the final power stages are fabricated in a GaAs HBT process. Measurements were carried out under the condition of a 3.4V supply voltage and a WCDMA (3GPP R99) modulated signal. Due to optimized broadband matching design, the Combo MB PA achieves a power-added efficiency (PAE) as high as 40% at a Pout of 28dBm over 824-915MHz in the HPM while keeping adjacent channel leakage power ratio (ACLR) less than -39dBc. In the LPM, PAE of 15 % at a Pout of 17dBm is obtained with ACLR of less than -40dBc. For 1850-1980MHz, the PA shows 35% PAE with ACLR of less than -37dBc at 28dBm of Pout in the HPM and 14% PAE at 17dBm of Pout in the LPM.