I'm trying to build a 38kHz IR blaster with 10 IR LED's. With the circuits I found here, I do not get enough range. I only get about 5 meters, while with a regular remote control I can reach 20 meters. With the circuit below I try to maximize the current through the LED's, say 60mA at a small dutycycle of 10-15%. I am however unsure how to calculate and regulate the current through the LED's. How do I do that?