Old 05-01-2015, 07:57 PM #1
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Default Laser driver 445nm 2A

I have a question for those who know me help:
this circuit should adjust the current on the load as a function of the reference voltage applied to the noninverting input of the operational amplifier and the inverting input should be a feedback for control of the current ... well: Why in my circuit if I change the voltage on the non-inverting input the current on the mOSFET does not vary but it vary if I change the voltage on the inverting input?



Last edited by killerwarrior982; 05-01-2015 at 08:04 PM. Reason: error
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Old 05-01-2015, 11:16 PM #2
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Default Re: Laser driver 445nm 2A

Please check the following voltages when the circuit is operating (with respect to ground, or power supply -):
Inverting input, non-inverting input, FET gate, FET drain, and power supply +
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Last edited by Cyparagon; 05-01-2015 at 11:18 PM. Reason: source is same as inverting... not needed
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Old 05-02-2015, 05:38 AM #3
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Default

I found Vcclaser = 4.98, Vccopamp = 12v vinverting = 0,08V, vnoninverting = 1.2V, vgate = 11.70V. but the same situation is if I force vnoninverting to 0V
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Old 05-03-2015, 11:55 PM #4
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Default Re: Laser driver 445nm 2A

Is "Vcclaser" the voltage across the laser, or the voltage from FET drain to power supply -? Are you saying you're powering the laser from 5V? Because that's not what the schematic calls for, and it won't work.

Looks like op-amp is working correctly.
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