说明：  本系统以直流电流源为核心，AT89S52单片机为主控制器，通过键盘来设置直流电源的输出电流，设置步进等级可达1mA，并可由数码管显示实际输出电流值和电流设定值。本系统由单片机程控输出数字信号，经过D/A转换器（AD7543）输出模拟量，再经过运算放大器隔离放大，控制输出功率管的基极，随着功率管基极电压的变化而输出不同的电流。单片机系统还兼顾对恒流源进行实时监控，输出电流经过电流/电压转变后，通过A/D转换芯片，实时把模拟量转化为数据量，再经单片机分析处理， 通过数据形式的反馈环节，使电流更加稳定，这样构成稳定的压控电流源。实际测试结果表明，本系统输出电流稳定，不随负载和环境温度变化，并具有很高的精度，输出电流误差范围±5mA，输出电流可在20mA~2000mA范围内任意设定，因而可实际应用于需要高稳定度小功率恒流源的领域。
(the system to DC current source to the core, MCU AT89S52 main controller, through the keyboard to set up DC power supply output current, set up to 1mA Stepping grades, digital control can be shown by the actual output current value and current setting. The system consists of programmable microcontroller digital signal output, after the D/A converters (AD7543) analog output. After Operational Amplifiers isolation, amplification and control of the output power base. With the power of the base voltage changes in the output current. SCM system also takes on the constant current source for real-time monitoring, after current output current/voltage changes, the A/D converter chip, real-time conversion from analog to the volume of data and then analyzed by the MCU, through data link in the )