The current accross the LED as function of the resistor value is given by the formulas. The circuit is valid para LEDs with 2.7 V of voltage fall. The maximum output current for the TTL gate is 40 mA.
The current accross the LED as function of the resistor value is given by the formulas. The circuit is valid para LEDs with 2.7 V of voltage fall. The maximum output current for the TTL gate is 40 mA.