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Programmable, very low noise current source

机译：可编程，低噪声电流源

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摘要

We propose a new approach for the realization of very low noise programmable current sources mainly intended for application in the field of low frequency noise measurements. The design is based on a low noise Junction Field Effect Transistor (JFET) acting as a high impedance current source and programmability is obtained by resorting to a low noise, programmable floating voltage source that allows to set the sourced current at the desired value. The floating voltage source is obtained by exploiting the properties of a standard photovoltaic MOSFET driver. Proper filtering and a control network employing super-capacitors allow to reduce the low frequency output noise to that due to the low noise JFET down to frequencies as low as 100 mHz while allowing, at the same time, to set the desired current by means of a standard DA converter with an accuracy better than 1%. A prototype of the system capable of supplying currents from a few hundreds of μA up to a few mA demonstrates the effectiveness of the approach we propose. When delivering a DC current of about 2 mA, the power spectral density of the current fluctuations at the output is found to be less than 25 pA/√Hz at 100 mHz and less than 6 pA/√Hz for f > 1 Hz, resulting in an RMS noise in the bandwidth from 0.1 to 10 Hz of less than 14 pA.
机译：我们提出了一种用于实现非常低噪声的可编程电流源的新方法，该电流源主要用于低频噪声测量领域。该设计基于充当高阻抗电流源的低噪声结型场效应晶体管（JFET），通过诉诸于低噪声可编程浮动电压源来获得可编程性，该可编程的浮动电压源允许将源电流设置为所需值。浮动电压源是通过利用标准光伏MOSFET驱动器的特性而获得的。适当的滤波和采用超级电容器的控制网络可将低频输出噪声降低至低噪声JFET所导致的低至低至100 mHz的频率，同时允许通过以下方式设置所需电流：一个标准的DA转换器，其精度优于1％。该系统的原型能够提供数百μA至几mA的电流，证明了我们提出的方法的有效性。当提供约2 mA的直流电流时，发现输出电流波动的功率谱密度在100 mHz时小于25 pA /√Hz，对于f> 1 Hz小于6 pA /√Hz，结果在0.1至10 Hz带宽内的RMS噪声小于14 pA。

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