LAB 2 - INTRODUCTION TO BIASING

Goal: To design a parallel circuit to power two different Light-Emitting Diodes (LEDs) with different ratings (LED1 is rated for 5V and 22.75 mA while LED2 is rated for 2V and 20 mA). Different resistors (R1 and R2) were used to adjust the right amount of current and voltage to power the LEDs.

Experiment:

Scheme of the circuit that was built in this experiment:



Calculations for the circuit:

Instead of using 176 ohms and 350 ohms resistors for R1 and R2, 220 ohms and 470 ohms resistors were used due to availability (measured resistances were 217 ohms and 457 ohms). We decided to use higher resistances to keep voltage supplied to LEDs below their maximum capacity.





Circuit was built on breadboard and experimental values were recorded:

Questions:

Conclusion:
Battery with higher voltage would give lower efficiency as higher resistances must be added to dissipate extra power from the battery (which becomes energy lost). In this experiment, 9V battery was used, and the circuit had a 42.8% efficiency. With lower battery voltage, lower resistances would be required, which would lower energy lost and raise circuit efficiency. Based on the available resistors, the most efficient circuit would have a 4V battery and use 100 ohms resistors for both R1 and R2. The efficiency of this circuit could reach up to 89.9% theoretically.