Question

HW 3 a : Power Supply LTspice Design a resistor/LED circuit such that the diode will be brightly let when V out i s 5 volts. Assume the diode has a forward voltage of 3.65V and a forward current of 20mA, when the diode is brightly emitting light. Note: You need to round your resistors to a whole number, as you cannot purchase non - whole numbers resistors.

Answer 1

Answer:

68 ohm

Explanation:

Output Voltage, Vout = 5 V

Forward voltage, Vf = 3.65 V

Forward current, If = 20 mA = 0.02 A

Let the resistance is R.

Use the formula

$I_{f}=\frac{V_{out}-V_{f}}{R}$

$0.02=\frac{5-3.65}{R}$

R = 67.5 ohm

R = 68 ohm ( approx.)