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In this brief, we present a dual-mode (high and low) power amplifier (PA) for fourth-generation long-term evolution (LTE) handset applications using a device switching technique to improve the efficiency at low output power. In particular, the effects of the gate voltage variation of the input and output switches on the amplifier performances are described. In addition, a bias control circuit for a dual-mode PA, which can provide the correct voltage to the input and output switches and can be effectively controlled by the mode control voltage, is also proposed. The bias control circuit, the mode switch, and the PA are implemented with the integrated pseudomorphic high-electron mobility transistor (pHEMT) and heterojunction bipolar transistor (HBT) technology on the same chip (i.e., bipolar field effect transistor process). A dual-mode PA with a gain of 27.2 dB, PAE of 34.5%, a ACLRE-UTRA value of -31.2 dBc, and error vector magnitude (EVM) of 2.97% has been achieved in high-power mode; whereas a 22 dB of gain, PAE of 19%, a ACLRE-UTRA value of -31.6 dBc and EVM of 2.84% were measured in the low-power mode with LTE uplink signals.
Circuits and Systems II: Express Briefs, IEEE Transactions on (Volume:58 , Issue: 12 )
Date of Publication: Dec. 2011