Introduction to Biasing

Motivational Design Problem:

We are to design a simple circuit that consists of a 9V Alkaline battery and two LEDs, with distinct voltage and current demands, which are used to indicate whether a device is on or off. We were to determine the most efficient layout for the circuit and the resistance needed in order to keep the LEDs from burning out.

Design Parameters:

The circuit is to be designed to handle a 9V Alkaline battery, one LED rated for 5V and 22.75mA and another LED rated for 2V and 20mA.

System Model:

Shown above is the circuit we built to model the desired system. In the configuration pictured it consists of a supply source set to supply 9V, a bread board with a red and a yellow LED installed, a resistor placed in front of both LEDs in parallel, a multimeter measuring Amps in one of the branches in front of the red LED and another multimeter which is measuring the voltage across the red LED.

Results:

By using the given requirements of the system and a few initial measurements we were able to use Kirchhoff's circuit laws in order to determine the values for the required resistors. 175.8 Olms were needed for the yellow LED's resistor while 360 Olms were required for the red one. However due to restraints on the available equipment we were forced to use a 150 and 360 Olm resistor respectively.