高稳定性数控恒流源设计

Design of numerical constant current source with high stability

在阻抗的测量过程中,为了提高测量的信噪比,通常需要使用高稳定性的恒流源,同时为了扩展测量的范围,也需要对恒流源进行控制调节,因此本文提出了一种高稳定性数控恒流源的设计方法。本文的恒流源通过对采样电阻端的电压进行差分放大反馈,一方面降低了共模噪声的干扰,提高了反馈精度,另一方面也降低了采样电阻端的热耗,为整个恒流源的长时间稳定性提供了保障,并且通过DAC可以实现对电流的线性调节。经过长时间的测试,该恒流源的输出电流的纹波小于0.1mA,不同电压下理论电流与实际电流误差在千分之一左右,具有较高的稳定性以及高的控制线性度等特点。

In order to improve the signal-to-noise ratio of the measurement,a constant current source of high stability is usually required,and to extent the measuring range,the constant current source can be used for adjusting and controlling,Therefore,this paper presents a highly stable constant current source method.Through the differential amplification and feedback of the voltage on the sampling resistor,on the one hand the common mode noise can be reduced and the accuracy of feedback can be improved,on the other hand also the heat consumption of the sampling resistor can be reduced,these aspects provide the guarantee for the constant current source of long time stability,in addition,the constant current source can be linearly adjusted by a DAC.After a long period of testing,the output ripple of the current is less than 0.1mA,and under different voltage the error of theory and actual in about one thousandth.So the constant current source is of high stability,and high control linearity.