With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compression at the low input power level is eliminated successfully.At 3.5V of supply voltage of the power amplifier after optimization exhibits 30dBm of maximum linear output power,43.4% of power added efficiency 109.7mA of a quite low quiescent bias current ,29.1dB of the corresponding gain,and -100dBc of the adjacent channel power rejection (ACPR) at the output power of 30dBm.
在对已发表的 Ga As HBT文献的研究中发现 ,其截止频率 f T 的理论计算结果比实验值小很多 ,而相应的文献中并没有给出 f T的计算结果。针对上述问题 ,文中对产生这种差距的原因进行了分析 ,认为由于速度过冲效应的存在 ,使得电子并非以饱和速度 Vsat渡越 BC结耗尽区 ,而是以更高的速度运动。基于上述理论 ,对产生截止频率误差的 BC结耗尽区电子渡越时间τsc进行了修正。利用修正后的公式对文献中的数据进行了重新计算 ,得到了令人满意的结果。
