Question

Which among the following is not a linear system?

The question was posed to me in an interview.

Asked question is from System Classification and Properties in portion Signals and Systems Basics of Signals and Systems

Answer 1

A nonlinear system is one where the output is not directly proportional to the input, i.e., it does not satisfy the principles of superposition and scaling. 

Some common examples of nonlinear systems include systems with exponential, logarithmic, or power-law relationships, or systems with memory that introduces nonlinearity.

Without specific options provided, a general example of a nonlinear system might be:

- A saturated amplifier (where the output doesn’t increase proportionally with the input once the input exceeds a certain threshold).

In contrast, linear systems follow the properties of superposition (additivity) and homogeneity (scaling), which means that their output for a weighted sum of inputs is the weighted sum of their outputs.

So, to answer the interview question, the correct response would depend on the options presented. For example, if one of the options is "a saturated amplifier" or "a system with a squared input term," that would be the nonlinear system.