Fixedvoltage

Fixedvoltage is a term used in electronics to describe a circuit or device that maintains a constant output voltage regardless of moderate changes in input voltage or load current, within specified tolerances. It is contrasted with adjustable or programmable regulators, where the output voltage can be changed by external components.

Fixed-voltage regulation is most commonly implemented with linear regulators or switching regulators that are designed to produce a predetermined voltage, such as 5 V or 12 V. Linear fixed regulators use an internal reference and pass transistor to keep the output at the target level, typically packaged as three-terminal devices (for example, 7805 or 7812). Switching fixed regulators use a DC-DC topology with feedback to hold the output constant, but with higher efficiency and the need for external inductor and diode components.

A separate, older approach uses a Zener diode as a fixed reference with a simple pass element, which offers limited regulation and efficiency but remains a teaching tool and a low-cost option in some low-power circuits.

Key specifications include output voltage tolerance, line regulation (variation with input), load regulation (variation with output current), dropout voltage (for linear types), quiescent current, and temperature coefficient. Linear fixed regulators are valued for low noise and simplicity but can dissipate more heat with large input–output differentials. Switching fixed regulators achieve higher efficiency but introduce switching noise and require external components.

Common examples are fixed 5 V regulators such as devices in the 7805 family in various packages, fixed 3.3 V regulators, and fixed-output switching converters labeled with the desired output. Fixedvoltage remains a fundamental concept in power supply design, underpinning reliable, predictable power for digital logic and analog circuits.