Hi, I have pic18f with ports can sink or source max 20-25ma. I like to light up a red led rated 2v at 20ma. Of course with less current foward volatge might not be 2v anymore proabaly less. What would be a good current and resitor value to drive the red led from the i/o pin without the use of a transitor just simple led with with the pin as the source. Thank you. I currently have it at 7-9ma with a 350 ohms. Is this current too much for the i/pin in the long run or not even close knowing the max is 20ma?

 

About 10mA would be a good choice. 350 Ohms seems about right. Max is 20mA so you are only at half.

If you run LEDs from a number of pins there is an issue of the TOTAL current taken (sum of all pins in use) exceeding the allowed limit for the chip.

 

I always keep a stock of 2N7000 Mosfet (FETLington). for those jobs.

 

Thank you @boostbuck yes not more than 10ma will be use and only using two leds two pins which will be less than 20ma in total, less 10ma in each pin. I seen many examples were they ususally just pick a 300 ohms or 330 ohms.

 

(FETLington)

What is a FETLington? All the disadvantages of FETs and Darlingtons?

 

What is a FETLington? All the disadvantages of FETs and Darlingtons?

It was a marketing ploy when Siliconix trademarked the Mosfet 2n7000.
The word "FETlington" is a reference to the Darlington-transistor-like saturation characteristic.
I have been using them since their inception.