A high efficiency and low Rx-noise three power mode power amplifier for W-CDMA handsets

This paper presents a high efficiency and low Receive-band noise power (Rx-Noise) three power mode power amplifier for W-CDMA handsets. The number of Switches in output matching circuit and bypass circuit are reduced to realize high efficiency in high-power mode operation. A switched feedback circuit is applied to the first-stage amplifier to achieve low Rx-noise performance. While satisfying adjacent channel power ratio (ACLR) of less than -40 dBc under the measurement condition of a 1.95 GHz W-CDMA (R99) modulated signal and a 3.4 V supply voltage, our developed amplifier achieves 28.25 dBm of high output power with power added efficiency (PAE) as high as 40% in the high power mode, 17.0 dBm with 23% of PAE in the middle power mode, and 7.0 dBm with 13% in the low power mode. Good Rx-noise characteristics of -136 dBm/Hz (190 MHz offset) at 28.25 dBm is achieved by using the switching feedback circuit.