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I am working on my graduation project to build a laser unit, i am supposed to control the power of laser diode when operating in pulsed mode and continuous mode. firstly, i had the pulses from "Arduino UNO" and connected it to a FET then i have a pulsed laser diode. secondly, i implemented a current constant driver which include a comparator "OP-AMP" , curent sensing resistor and FET, then i can control the current of laser diode butt it is not pulsed. The question here is how can i make an accurate constant current driver controlling the laser diode by digitally (by Arduino) with the ability to work in CW or pulsed mode.

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    \$\begingroup\$ Show the schematics of your circuits, and specify the components you're using. \$\endgroup\$ – CL. Dec 19 '15 at 16:10
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    \$\begingroup\$ Also, you need to specify the minimum pulse width you need to control and your target for the accuracy of your "accurate constant current driver". \$\endgroup\$ – The Photon Dec 19 '15 at 16:49
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Mosfets are an answer. They do make great current sources and scaling is by size. To be honest I don't know how fast you need to pulse this, but I'm going to give you a part that is both a CC driver and a PWM. You really don't want to make that circuit discretely. CAT4101 from OnSemi. Use a make-before-break digi-pot to change the constant current bias and use pwm for... pwm!

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