Hello,
I am working on interfacing a laser diode into my system. Based on my research, I understand that laser diodes are finicky and easy to damage. I was hoping to use a TI opamp to act as the automatic power control on the laser diode. Does anyone have any suggestions or application notes that they suggest to get up an running?
Thanks,
Alex
Hello Alex,
My understanding is that laser didoes are driven usign high-speed current sources.
You can use the OPA861 for low power application as it will give you 80MHz bandiwdth. This OPA861 solution will be very limited in output drive however. For higher output drive capability, you will have to look into driving a fast power transistor as a current source with a high-speed amplifier. We have several amplifiers that would fit this function. It is possible to use an amplifier such as the OPA2673 to create a 100MHz current source with a 1A output drive.
Best Regards,
Xavier
Xavier,
I think the OPA861 will be good for my application.
Now I need to consider the power supply. I know that the laser I have in mind will probably not take more than 130 mA max. I was thinking of getting a linear regulator with high PSRR and a slow start function. My understanding is that laser diodes are easy to damage and transient voltages and currents can be a problem. I was thinking of the TPS7A4901 linear regulator. It seems to have the enable, high PSRR, and soft start functionality I want. However, I am a bit concerned about running the current up to 130 mA when the regulator can't source more than 150 mA.
Do you have any suggestions on this?
Alex,
On +10V, the OPA861 can source/sink ±15mA, on +5V, this goes down to ±8mA, so to achieve 150mA drive, you will have to use 10x OPA861 in parallel. Each OPA861 will consume ~6mA quiescent current.
The maximum number of OPA861 the TPS7A4901 can supply current to is 7x. Say 5x for some margin. It should be possible to have 2 section with each 1 TPS7A4901 and 5x OPA861 to drive 1/2 of the maximum current the laser diode your are considering.
The TPS7A8001 could be considered for +5V or the positive supply in the dual supply ±5V if sourcing current to the diode.