Physics Homework Solution Library

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Physics Homework Problem Code: PHP-01

A basic LED driver circuit is comprised of a 5 volt source a 2 kohm potentiometer and a LED. The LED is forward biased. The LED manufacturer indicates a maximum current rating of 20 mA at a diode voltage drop of 1.9 volts?

a) What is the minimum value of resistance the potentiometer can be adjusted to before damage to the LED occurs?

b) What is the nominal resistance of the LED with this condition?

c) Draw a schematic diagram illustrating the addition of a component that will protect the LED in the event that the pot is adjusted below a safe level?

Physics Homework Problem Code: PHP-02

A red LED is operated in pulse mode with 80 mA of peak current applied at a duty cycle of 20%. Vd is 1.9 volts?

a) Determine the average LED current?

b) Assuming a dynamic resistance of 50 ohms calculate the average power dissipation of the LED component?

Physics Homework Problem Code: PHP-03

A silicon junction generates an electron differential of 1.09 eV. What radiated wavelength will propagate with this condition?

Physics Homework Problem Code: PHP-04

Observe the diagram of figure 1-1. Vcc = 12 volts, R2 is 50 ohms and Vz is 4.8 volts. Calculate the emitter and LED current. Determine the value of VCE when Rnom. of the LED is 30 ohms?

Physics Homework Problem Code: PHP-05

What is the role(s) of a plastic dome over an LED substrate system?

Physics Homework Problem Code: PHP-06

A particular LED has a reference intensity of 12 mcd at a reference current of 10 mA. The component has a peak current of 100 mA with an efficiency of 1.5. A pulsed operation implements a duty cycle of 20 percent. Determine the average intensity of the LED?

Physics Homework Problem Code: PHP-07

Provide a basic labeled sketch illustrating the substrate and associated layers of an LED (assume a GaAsP n-layer). Idicate where the flux escapes the component?