Solving a Diode Circuit with Varying Resistances

[funsty101]

Homework Statement

A diode with reverse saturation current of 1pA and an ideality factor of 1.15 is connected in series with a resistance of 200ohms and connected to a 5V DC supply voltage. Find the current flowing in the diode at a temperature of 290K? How does the current change when a 800ohm resistance is placed in parallel with the diode?

Homework Equations

The Attempt at a Solution

 

[Defennder]

Well you could start off by providing the equation for current flow I_D in a diode.

 

[Mene]

To solve this diode circuit, we can use the Shockley diode equation:

I = I0 * (e^(qV/kT) - 1)

Where I is the diode current, I0 is the reverse saturation current, q is the electronic charge, V is the voltage across the diode, k is the Boltzmann constant, and T is the temperature in Kelvin.

Plugging in the given values, we get:

I = (1e-12A) * (e^((1.602e-19C)(5V)/(1.38e-23J/K)(290K)) - 1)

Solving for I, we get a diode current of approximately 1.03mA.

When an 800ohm resistance is placed in parallel with the diode, the current flowing through the diode will decrease. This is because the addition of the parallel resistance creates a new path for current to flow, reducing the overall resistance of the circuit. Using Ohm's Law (V=IR), we can calculate the voltage drop across the parallel resistance to be 3.125V. This means that the voltage across the diode will be reduced from 5V to 1.875V, resulting in a lower current flow. The exact current value can be calculated using the Shockley diode equation as shown above.