Lab 2: Introduction to Biasing

Intro:

The purpose of this lab is to use biasing to establish the correct voltage and current across two LEDs connected in parallel to a battery.

Experiment:

Data:

I_R1= 22.75mA   I_R2 = 20Ma

V_R1= 4V            V_R2 = 7V

Using R=V/I

R1=175.82       R2 = 350

The closest Resistances we will use are 220 ohms and 470 ohms.

            I_LED1      V_LED1     I_LED2      V_LED2     I_Supply

1          .47mA  6.28V   .54mA  2.236V X

2          .40mA  6.22V   x          x          .40mA

3          x          x          2mA     2.14V   2mA

 Analysis:

The life for an LED attached 9 volt batter at 0.2 A-hr

            LED = .2/.00047 = 425.5 hours

The error

LED1 = (.47-40)/.40 = 17.5%

LED2 = (.54-2)/2 = 73%

Efficiency = P_out/(P_out + P_lost)

P_out = i*V= .006768

P_lost = i*V= .0041

Efficiency = 71.76%