There are two main ways to solve circuits containing diodes: the graphical method and the diode approximation.
Graphical Method
The image below shows a simple circuit with a diode connected in series with a resistor. Suppose the voltage through the diode is Vd, and the current flowing through this circuit is Id. We can write out the equation using Kirchoff’s law, the sum of the voltage across each component is equal to the total voltage applied to the circuit. This equation gives us the linear relationship between Vd and Id, this line is called the load line. By finding the point of intersection of the load line and IV curve of the diode, we can easily find what exactly is the current and voltage across the diode.
Diode Approximation
We will assume that whenever the diode is forward biased, then the voltage across the diode will be 0.7 volts and whenever it is reverse biased, the diode will simply act as an open switch.
