LMV358: output current

Hi Yannick,

60mA is the short circuit current, when the output voltage is broken down to 0V. This current cannot be used for driving a LED.

Have a look at figure 14 of datasheet to see how the output voltage of LMV358 changes with the output current. This helps to dimension the current limiting resistor.

An example: At 5mA output current the maximum output voltage of LMV358 is 5V - 0.1V = 4.9V. With a voltage dropping across the LED of 1.6V at a LED current of 5mA, 4.9V - 1.6V = 3.3V must drop across the current limiting resistor. So, a current limiting resistor of R = 3.3V / 5mA = 660R must be chosen. 680R is close enough to it.

By the way, section 9.2.10 of datasheet of LMV324-N shows how to drive a LED.

Kai

OK and so if I have a LED of about 1.45V @ 100 mA, does the LMV358 can drive it ?
I can see very well on the picture.

OK and if I use TLV342 with +5Vdc supply ?

Hi Yannick,

the TLV342 doesn't look much better. Have you had a look into its datasheet?

What are you planning to do? Do wou want to control the LED current? Then you should look for a current source. You can add a transistor to the OPAmp to build a simple current source.

Kai

Yes I see on the datasheet fig 6 that the TLV342 can drive more than 100 mA.
But you're right, I can try with a transistor to make a current surce.