由于外腔半导体激光器系统中的核心部分——激光器受外界环境影响较大，在装配或工作中极易受到电压、电流和静电荷的影响而损坏．为减少由于电路不稳定产生的激光器损坏，在借鉴各种传统的恒流源电路实现方式的基础上，运用反馈恒流原理，慢启动慢关闭原理，利用场效应管特性，给出一种高准确度恒流电路实现方式．将此电路直接运用于中心波长1550 nm激光器作为驱动电路，工作稳定、输出电流受负载影响很小且输出准确度达到同行业先进水平．电流稳定达到0．01%以上．此电路实现方式简单，实用性较强，对整个电路做出了实验仿真和测试，很好地解决了由于驱动电流不稳造成的激光器损坏的问题．

The laser diode which is the key of external cavity laser diode (ECLD) is a very tender part. It is easily damaged by the impact of the voltage,current and static when its assembly and running. To avoid the damage,the feedback constant current theory,low startup theory,low close up theory and MOS effect transistor speciality are applied to realize a new method of high-resolution constant current circuit,after some traditional methods used for reference. The new method is applied for the high resolutional external cavity semiconducter laser diode of the 1550nm wavelength to drive the current constantly. The resolution of drive circuit can be achieve in high level and be above 0.01%. The project is simulated by Protel DXP tool,designed by the PCB circuit,and applied to the laser driver circuit system,which has proved the constant current model can avoid the damage for drive current fluctuation availably.