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利用OPA2140搭建的电流源问题

Other Parts Discussed in Thread: OPA140, OPA2140

最近工作需要,搭建了一个0-24mA的电流源,用OPA2140和OPA140构成,设计原理图如下:仿真时没有问题,现在做出来的pcb有点小问题:

1、单电源供电时(正12V)时,输入0-2V,输出电流可在0-24mA可调;

2、双电源供电(正负12V)时,输出电流产生了0.25-0.3mA的增量。比如1V输入时,输出电流为10.3mA左右。1-2V输入时均存在该现象;且双电源供电时,输出电流最多到18mA就不能增加了。很奇怪目前还没找到原因。

希望有大佬指点下~~