介绍了一种压控电流源电路的工作原理,该电路在传统Howland电流源电路的基础上进行改进,采用差动运放电路结构构建电压-电流转换电路,利用FPGA控制DAC输出不同的电压,实现4~24 mA电流输出。论证和分析了运放、DAC、电阻网络等因素对电流输出精度的影响,为器件选型、电路设计提供了指导。提出采用线性拟合方式进行补偿,有效提高了电流输出精度。经过测试,基于SGM8249运放搭建的恒流源电路在-30~70 ℃温度条件下,电流输出在4~24 mA范围内,最大误差不超过0.03 mA,相对满量程误差小于0.15%,满足实际工程应用中电流输出精度小于0.3%的需求。

This paper introduces the working principle of a voltage-controlled current source circuit, which is an improved version of the traditional Howland current source circuit. It employs a differential operational amplifier (op-amp) circuit structure to construct a voltage-to-current conversion circuit. By using an FPGA to control the DAC output to generate different voltages, the circuit achieves current output ranging from 4 mA to 24 mA. The paper analyzes the impact of factors such as the op-amp, DAC, and resistor network on current output accuracy, providing guidance for component selection and circuit design. A compensation method using linear fitting is proposed, effectively improving current output accuracy. The constant current source circuit built using the SGM8249 operational amplifier was tested under temperature conditions ranging from -30℃ to 70℃. Within the current output range of 4 mA to 24 mA, the maximum error did not exceed 0.03 mA, and the relative full-scale error was less than 0.15%, meeting the requirement of current output accuracy less than 0.3% in actual engineering applications.