为了保护激光器工作并省去相应复杂的高速保护电路，设计了同步可调恒流管串联式激光器恒流源。采用模拟电路的方案实现两恒流管同步调整，使在整个调整范围内，不仅都能保持在恒流区域工作，而且其输出电流基本相等；激光器在400mA工作时由任一晶体管瞬时损坏引起的电流增大只有15mA。结果表明，用同步可调恒流管串联式电路制作的激光器恒流源具有很好的恒流特性和保护性能。

The accident damage of the present semiconductor laser constant current source often damages the expensive semiconductor laser directly. In order to protect the laser working normally and save the complex high-speed protection circuit,the synchronously adjustable constant current tube tandem type laser constant current source is designed. It adopts two constant current tubes to be adjusted synchronously. Both of them can be kept working in the constant current area,and their output currents are equivalent to a large extent in the whole adjustment range. When the laser is working in 400mA,the current aggrandizement caused by the momentary damage of any transistors is only 15mA. It is concluded that the laser constant current source made of the synchronously adjustable tandem constant current tube has high constant current characteristic and protective property.