Question

For a green LED, calculate an appropriate value for a

current-limiting resistor to maintain ~10 mA with a CMOS logic HIGH value of ~5 V.

Answer 1

To calculate the current-limiting resistor for a green LED with a 5V supply and 10 mA current, subtract the LED's forward voltage from the supply voltage, then use Ohm's Law. In this situation, a resistor of approximately 300 ohms is suitable.

Step-by-step explanation:

To calculate the appropriate value for a current-limiting resistor for a green LED operating with a CMOS logic HIGH value of approximately 5V and maintaining a current of around 10 mA, we use Ohm's Law, which states that the resistance (R) can be calculated as the voltage (V) divided by the current (I), or R = V / I. Since LEDs have a forward voltage drop, typically around 2V for a green LED, we subtract this from the supply voltage to determine the voltage across the resistor:

Vresistor = Vsupply - Vforward = 5V - 2V = 3V

Now, converting the desired current into amperes (10 mA = 0.01 A), we can solve for the resistor value:

R = Vresistor / I = 3V / 0.01 A = 300 ohms.

Therefore, a 300-ohm resistor would be appropriate to maintain a current of approximately 10 mA for a green LED with a 5V logic HIGH supply.