# OP-Amp Power Supply Current

1. ## OP-Amp Power Supply Current

Hello,

I am using a dual supply power amplifier op-amp of +/- 5V to drive a laser at 1.2A. I wanna calculate the power supply current. For that I have added the quiescent current and the load current of 1.2A. Is this the correct way?

I am using two different regulators one of +5V and another one of -5V. How much current will be drawn from each regulator?

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2. ## Re: OP-Amp Power Supply Current

I guess the laser current will either run from V+ to GND or V- to GND, depending on your circuit. Means that only one power supply must be designed for high current.

Take care that the driver circuit doesn't apply reverse voltage > 2V to the laser diode.

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3. ## Re: OP-Amp Power Supply Current

Originally Posted by Manu_work
I am using two different regulators one of +5V and another one of -5V. How much current will be drawn from each regulator?
Hi,

If you mean linear voltage regulators, hopefully the datasheet will state in the electrical characteristics how much ground pin current is drawn at different loads, and there should also be a graph showing the same information, from which you can calculate or approximate the expected value for a load of 1.2A. As previously mentioned, if the laser only draws current in one direction, then that regulator will have the highest ground pin current. Based on what the op amp will do, you can calculate what both regulators will use in current.

I might be wrong, but I think for a total current budget for a power supply, if there are a lot of other components, like resistors, they all consume (a very small amount of) power that you could add, but I doubt that makes much difference to a circuit drawing 1.2A so would be a waste of your time as presumably the power supply is quite powerful.

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