I need a clear explanation on the terms linear and non linear (components, circuits, )

 

Any relationship between two quantities that can be graphed as a straight line is a "linear relationship": eg. Voltage is a linear function of current in a resistive load. Why?
V = R x I. R, the resistive load is constant,

Any relationship between two quantities that cannot be graphed as a straight line means the quantities are not related, or if they are related then the relationship is non-linear. eg. The drain current in a JFET is proportional to the square of the gate to source voltage. That is the current is a quadratic (non-linear) function of the gate to source voltage.

That's about it.

 

Linear means one function is linear (directly proportional) with respect to another function, e.g. the current through a metal conductor is directly proportional to the voltage across the resistance.

Non-linear means the two functions are not linear (not directly proportional) to each other.
Thus the current through a diode is a logarithmic function of the voltage across it so is (very) non-linear.

If an amplifier is linear then the output is a direct replica of the input (no distortion) except for any difference in amplitude due to the amplifier gain.
If the amp is non-linear (has distortion) then the output is not a direct replica of the input.
The distortion value determines how much the output deviates from the input.

 

I need a clear explanation on the terms linear and non linear (components, circuits, )

Hi,

linear and non linear are mathematical concepts. How they apply to real life circuits can vary.

In the strictest sense linear means a straight line through the origin. That means even an offset can make it non linear. This is often stretched to include an offset though, but it depends on the application if you can get away with this or not.

Resistors are considered linear in almost every application, while inductors and capacitors are lnon linear in time but linear in the frequency domain.

Another example is PWM, which in the averaged model would be considered linear but in the time domain would have to be considered as non linear.

What all this means is that linear and non linear can not sit all by themselves there must be an application associated with the problem in order to be able to classify something as linear or non linear. The application restricts the view we can take, with attention to the describing function. If the function is non linear in that domain, then it would be non linear, but if the function was linear in that domain then of course it would be considered linear.

There are classifications associated with certain equations that deem them either linear or non linear. Again this a mathematical concept void of any application as of yet. Knowing the classification of the equation can guide us into a solution method which is particular to that equation. In this way the idea of linear or non linear is a known quality before we even solve the equation and knowing that helps us find a solution especially when we find a linear one because linear equations are almost always easier to solve then non linear ones.

What this suggests is that the idea of linear or non linear can be applied to an equation directly, but to apply it to a real physical situation or object we have to know more about the application such as the domain, and that is simply because a real application can have more than one mathematical representation.

Also, sometimes a component is considered linear simply because there exists at least one representation that is linear. I dont think that is the right way to explain something, but that's been done in the past. An example is a capacitor which is often quoted as being a 'linear' element. It's not linear in time, but because it is linear in frequency and we can transform the domain from time to frequency it is often just called a linear element.

Another view is the view of the actual solution itself. A capacitor excited by a constant current source will show a linear solution even in time. Excited by a ramp current however will show a non linear solution in time.