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This paper presents a hybrid supply modulator (SM) including a buck-boost (BB) converter, which has wide battery operating range for cellular envelope tracking (ET) applications. The proposed SM supports both ET and average power tracking (APT) mode depending on the power amplifier (PA) output power level. The output voltage swing of SM is boosted up to 4.5 V by the integrated BB converter as a supply of a linear amplifier. The dynamic-controlled BB output increases ET operating range, whose efficiency is higher than that of APT, by scaling down the supply voltage of the linear amplifier according to the PA output power level. A selective supply voltage of a switching amplifier and a reverse current sensing circuit are employed to prevent the reverse current through the power inductor of the switching amplifier. The proposed automatic current ratio controller between the linear amplifier and the switching amplifier provides the robust performance against the battery voltage variation of 3.2–4.6 V. A programmable bias current of the class-AB output buffer and a programmable hysteretic comparator are employed to achieve the optimum efficiency and bandwidth depending on the operating signal bandwidth. Optimal control for low signal bandwidth applications such as voice over Long-Term Evolution (LTE) with the selective notch filter provides the maximum efficiency of 88.2% with −135 dBm/Hz output noise. The proposed SM supports the LTE 20-MHz envelope signal with 78% efficiency at 800-mW output. Adapting the designed SM to frequency-division duplex Band3 radio frequency PA, the implemented ET-PA achieves the power added efficiency of 41.6% at 27-dBm PA output power while achieving −40 dBc of E-UTRA ACLR and −137 dBm/Hz of receiver band noise. The chip is implemented in the 0.13- $\mu \text{m}$ CMOS process, and the die size is 5 mm2. [ABSTRACT FROM AUTHOR]

This paper presents an envelope tracking power amplifier (ET PA) using a dual-mode supply modulator for handset application. The supply modulator has a combined structure with a linear amplifier and a switching amplifier. The dual-mode supply modulator operates in high-power mode and low-power mode by providing the supply voltage of the linear amplifier of 5 and 2.5 V, respectively. For 1.74-GHz long-term evolution signal with 10-MHz bandwidth, 6.44-dB peak-to-average power ratio, and 16-quadrature amplitude modulation, the ET PA delivers a power-added efficiency (PAE) of 39.8%, an evolved universal terrestrial radio access adjacent channel leakage ratio (\E-UTRAACLR) of -35.7 dBc, and an error vector magnitude (EVM) of 3.81% at an average output power of 27 dBm. The ET PA also delivers a PAE of 22.6% at an average output power of 18 dBm, which is 6.6% higher than that of the conventional ET PA and 13.1% higher than that of the standalone PA. The supply modulator is connected to a drive stage and a power stage of the PA simultaneously for further enhanced efficiency at a power back-off region. The dual-mode two-stage ET PA delivers a PAE of 38.1%, an \E-UTRAACLR of -32.9 dBc, and an EVM of 4.74% at an average output power of 27 dBm. The dual-mode two-stage ET PA also delivers a PAE of 26.3% at an average output power of 18 dBm, which is 7.8% higher than that of the conventional two-stage ET PA and 16.7% higher than that of the standalone PA. [ABSTRACT FROM PUBLISHER]

This paper describes circuit design and measurement results of a bipolar field-effect transistor monolithic microwave integrated circuit power amplifier (PA) module operating with a 2.5-V low reference voltage ( Vref) and a 2.8-V low collector supply voltage ( Vcc). While covering 824–925-MHz broadband CDMA operation at 2.8 V of Vcc, the PA allows a 1.1-V low Vcc and 18-dBm output power ( Pout) operation. This is realized using an on-chip step quiescent current control scheme depending on Vcc. In addition, an input high electron-mobility transistor single-pole double-throw switch is integrated on the PA die for selecting 800/900-MHz operating bands, thereby providing easy connectivity between a transmit surface acoustic wave filter and the PA. Measurement results under the 2.8/1.1-V Vcc and 2.5-V Vref bias conditions show that the PA meets J-CDMA/W-CDMA power and distortion specifications sufficiently over a wide temperature range from -20 ^\circC to 85 ^\circC while realizing a broadband operation ranging from 824 to 925 MHz. For J-CDMA (IS-95B) modulation, the PA can deliver a 28-dBm Pout, a 36% power-added efficiency (PAE), and a -50-dBc adjacent channel power ratio, while a 29-dBm Pout, a 38% PAE, and a -40-dBc adjacent channel leakage power ratio (ACLR) are achieved for W-CDMA (3GPP R99) modulation. Under 3:1 load mismatching condition, the PA also suppresses ACLR of less than -36 dBc while keeping a forward power of 27.5 dBm. Moreover the PA is capable of delivering a 18-dBm Pout and more than 26% PAE under 824–925-MHz and 1.1-V J-CDMA modulation test conditions. To the best of authors' knowledge, this is the first report on a broadband production-level CDMA PA operating with low Vref and low Vcc. [ABSTRACT FROM PUBLISHER]