A linear circuit is an electronic circuit in which the relationship between the input and output signals follows the principles of linearity. Linearity implies that the output response is directly proportional to changes in the input, making the circuit behavior predictable and mathematically describable.

Let’s consider an example of a simple voltage divider circuit, which is a linear circuit:

In this circuit, Vin is the input voltage, R1 and R2 are resistors, and Vout is the output voltage. The output voltage, Vout, is determined by the voltage divider formula:

�out=�in×�2�1+�2Vout​=Vin​×R1+R2R2​

This formula shows that the output voltage is directly proportional to the input voltage and depends on the ratio of the resistances R1 and R2. If you double the input voltage (Vin), the output voltage (Vout) will also double, maintaining a linear relationship.

The key characteristic of linear circuits is that they follow the superposition principle, which states that the response to a sum of multiple inputs is the same as the sum of the responses to each individual input. This makes linear circuits easier to analyze and design compared to nonlinear circuits.