| Power amplifier is the key component of the wireless communication. This paper is focused on the design of power amplifier circuit based on GaAs HBT. The main works of this paper are introduced in the following:(1) The mechanism of self-heating effect and current gain collapse is discussed, ballasting resistor is presented to improve the self-heating effect.(2) A RC stability circuit is employed to raise the stability K factor effectively, achieve unconditional stability.(3) An adaptive linear bias circuit is employed to compensate the decline of base-emitter junction voltage of power amplifier, meanwhile a temperature compensation circuit in bias circuit could suppress the shift of the bias point with temperature.This paper presents a5.8GHz GaAs HBT MMIC power amplifier tested on PCB. The power amplifier exhibits a power gain S21=27dB, the gain flatness is2dB, the reverse isolation ratio S12=-50dB, the S11and S22<-10dB, the1-dB compression point of the power amplifier is26.9dBm, and the power-added efficiency (PAE) is29%, the second harmonic generation coefficient is-36.2dBc, the third intermodulation distortion coefficient (IMD3) is-26.6dBc, the Adjacent Channel Power Ratio(ACPR) is-31.5dBc, the size of the chip is3.2*1.4mm2. |
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