改善放大器噪声性能的SiGe HBT几何参数优化设计

研究有源器件SiGe HBT的几何参数对单片低噪声放大器(LNA)噪声性能的影响.基于0.35μm SiGe BiCMOS工艺,研制了4款采用不同几何参数的SiGe HBT LNA.实验结果显示,在给定的偏置条件下,当发射极宽长比较小时,小范围改变发射极宽度对噪声系数(NF)改善微弱,但适当增长发射极条长和增加发射极条数明显降低了NF,且不牺牲增益.另外,与采用其他几何尺寸的SiGe HBT LNAs相比,选用器件发射极面积为A_E=4μm×40μm×4的LNA性能最优,在0.2~1.2 GHz内获得低至2.7 dB的噪声系数,高达26.7 dB的相关增益和最接近于50Ω的最佳噪声源阻抗.由于没有使用占片面积大的电感,放大器芯片面积仅为0.2 mm².

Geometry Optimization of SiGe HBTs for Noise Performance of Amplifier

The influence of various geometry sizes of SiGe HBTs on noise performance of the monolithic low noise amplifier(LNA) is investigated in this paper.Four types of LNAs using SiGe HBTs with different geometry parameters are fabricated in a 0.35 μm SiGe BiCMOS process technology.The measurement data indicates that at a given bias condition,a smaller emitter width slightly improves the noise figure(NF) if the ratio of emitter width to emitter length is small,however a proper longer emitter width and less emitter strips can significantly improve the overall NF without significant the gain degradation.Geometry scaling data show that the optimal LNA using SiGe HBT with AE=4 μm×40 μm×4 has the minimum NF of 2.6 dB,the maximum associated gain of 27.4 dB and the optimum noise source resistance of nearly 50 Ω over 0.2-1.2 GHz compared to other device geometries.The die areas are only 0.2 mm2 due to the absence of inductors.