I have read with interest about the National Semi op-amp LME49990. It has excellent low noise and I want to use it to drive a 125 ohm load. Below is part of the LME49990 data sheet:
OUTPUT CHARACTERISTICS
ISHORT Output Short-Circuit Current VCC = ±18V +75/-70 +55/-50 mA (min)
IOUT Output Current VCC = ±18V, RL = 600Ω 26 24 mA (min)
I am not working into a 600 ohm load but 125 ohms; I will apply 5 VDC maximum so the current may be up to 40 ma. Is there any characterization data to show how
much voltage will be dropped inside the LME49990 or what the max linear I out current can be? I suspect that it can supply current more than 24 ma into a lower load resistance.
From a Power dissipation and heat consideration, there is not a problem. From the data sheet, the op-amp in a SOIC package has a Theta JA of 145 degrees C/ Watt. So with a
Temperature rise of 65C, then the power dissipated can be 0.48 watts. So the IC is safe even with 12 VDC applied to the power pin and 5 VDC on the output pin and up to 68 ma
of current being sourced from the op-amp. The op-amp will, of course, current limit before the 68 ma but from a heat standpoint the op-amp is safe. Is there any characterization
data that is not shown in the data-sheet that shows I out vs Vout? [that is shown in other op-amp data-sheets]
