# Op Amp Fundamentals

I have a question regarding op amp fundamentals that I am struggling with. It is about the input current for an op amp. I am designing a simple current amplifier using the OPA548. My input is 1V pk-pk and I'm outputting 10V pk-pk and pushing around 333mA. I'm also powering the op amp with +- 12V. Without violating the laws of physics, how can it be proven for my circuit that power in = power out. What is the typical input current for an op amp? I understand that the input current is theoretically zero but then how does the power in = power out? The reason I am asking this is because I am using a 12V power supply that outputs around 1.3 amps to power both an NI module and this op amp. I am wondering if the power supply will output enough current for both the NI module and the op amp? Do I have to be concerned with the current flowing from the rails? Is that current theoretically suppose to be zero? I know my understanding of how an op amp works is not very good and I would appreciate your help in clearing this up for me. Thanks in advance.

• Current from the rails is not theoretically zero, only the current at the + and - inputs.
– Null
Feb 19, 2015 at 19:53