四极质谱检测中复合放大器的低噪声高带宽设计  

Low-noise and wide-band design of composite preamplifier in quadrupole mass spectrometer

作　　者：吴保军[1] 江游[1] 高印寒[2] 方向[3] 

机构地区：[1]吉林大学仪器科学与电气工程学院,吉林长春130022 [2]吉林大学测试科学实验中心,吉林长春130025 [3]中国计量科学研究院,北京100013

出　　处：《光学精密工程》2008年第9期1767-1772,共6页Optics and Precision Engineering

基　　金：国家"十五"科技攻关项目(No.2004BA210A04)

摘　　要：四极质谱峰信号是10^-11～10^-6A级的微弱电流，并且快速变化，所以在大动态范围内实现放大器的低噪声和高带宽是设计关键。本文设计了一种开环增益可调整的同相输入复合跨阻抗放大器，并分析了开环增益对信号和噪声的影响。在较低放大倍率时，改变开环增益后放大器会降低自身产生的噪声，实现低噪声；在较高放大倍率时，改变开环增益后放大器能扩展被极高阻值的反馈电阻和寄生电容降低的信号带宽。实验结果表明：与反相输入复合放大器相比，同相输入复合放大器在10^6～10^7V／A放大时能降低5％～30％噪声，在10^8V／A放大时可扩展带宽1．8倍并提高10％～15％质谱峰强度。在10^6～10^8V／A大动态范围内，同相输入复合放大器可降低噪声和扩展带宽，提高了四极质谱峰的信噪比、灵敏度和分辨率。To measure the ultra low current in a quadrupole mass spectrometer （QMS） by a preamplifier, low noise and wide bandwidth is the key to this system for its current is from 10^-11 A to 10^-6 A and varies quickly. So a Non-inverting Input Composite Preamplifier （NIICP） is designed, and the effect of the open-loop gain on optimizings the frequency responses of signal and noise is analyzed. NIICP can optimize the open-loop gain to reduce intrinsic noise in the lower magnification and to recover high frequency signal damped down by the low pass transfer function of large feedback resistance and parasitic capacitance in the higher magnification. Compared with Inverting Input Composite Preamplitier （IICP） in the commercial QMS, the NIICP can reduce noise by 5%-30% in the 10^6-10^7 V/A magnification,and can expand signal bandwidth by 1.8 times and increase MS peak amplitude by 10% -15% in the 10^8 V/A magnification. Experimental results show that the wide-band low-noise NIICP improves the signal-to-noise radio of MS peak in large dynamic range of 10^6 -10^8 V/A.

关 键 词：四极质谱 跨阻抗放大器 低噪声 高带宽 

分 类 号：TH843[机械工程—仪器科学与技术]