# Why is a linear power supply called linear ?

## Why is a linear power supply called linear ?

A linear power supply is named as such because of the linear relationship between the input voltage, output voltage, and current. In a linear power supply, the input AC voltage is first transformed to a lower AC voltage (if needed), rectified to DC, and then regulated to a stable DC output voltage using linear regulators. The term “linear” refers to the fact that the regulation process involves linear devices such as resistors, capacitors, and linear regulators that maintain a constant output voltage by dissipating excess energy as heat. This design results in a smooth, continuous adjustment of voltage without abrupt changes or switching noise.

Linear regulators are called linear because they use linear components (typically transistors operating in their active region) to regulate and stabilize the output voltage. The operation of linear regulators involves adjusting the resistance to maintain a constant output voltage relative to the input voltage. This continuous adjustment ensures a stable output voltage but also results in lower efficiency compared to switching regulators, as excess energy is dissipated as heat.

To determine if a power supply is linear, look for characteristics such as the absence of switching noise during operation, smooth and ripple-free output voltage, and the presence of a bulky transformer and heat sinks (indicative of linear regulator components). Linear power supplies are generally heavier and larger due to their design and the need for heat dissipation.

A linear power supply is characterized by its use of linear regulators to regulate the output voltage. Linear regulators maintain a constant output voltage by dissipating excess energy as heat. In contrast, a non-linear power supply typically refers to switch-mode power supplies (SMPS) that use high-frequency switching circuits to convert and regulate input voltage efficiently. SMPS achieve higher efficiency by rapidly switching semiconductor devices (such as transistors) between on and off states, minimizing energy loss and heat dissipation.

The difference between linear and variable power supplies lies primarily in their regulation method and versatility. A linear power supply uses linear regulators to maintain a constant output voltage, offering precise and stable voltage regulation but with lower efficiency and higher heat dissipation. In contrast, a variable power supply may refer to either a linear or a switch-mode design that allows the user to adjust the output voltage within a specified range. Variable linear power supplies provide smooth adjustment of output voltage but are generally bulkier and less efficient than variable switch-mode power supplies, which offer higher efficiency and lighter weight due to their switching operation.