Linear Voltage Regulators
Linear voltage regulators are components (with or without associated circuitry) that provide a stabilised output voltage from a potentially unstable power supply source. They may also act to step up or step down a difference between supply and output voltages, with additional functions possible through added circuitry.
As well as voltage regulation, current regulation is possible with a change to some of the additional components.
The 78xx series of voltage regulators are commonly used to provide a stable output voltage from a slightly higher input voltage.
The 79xx series of voltage regulators perform in pretty much the same way, but are intended to output a negative voltage.
The LM317 provides an adjustable solution filling the gap where a fixed voltage regulator isn't available, or where a variable voltage supply is required.
Many other linear voltage regulator families exist with features such as:
- lower drop out voltage (the difference between the input voltage and the regulated output voltage)
- higher power capacity (greater than the typical 1A limit, although this often means larger heat sinks anyway)
- other voltage ranges and precision voltage levels, such as 3.3V required for microcontrollers
Efficiency is a major drawback of linear voltage regulators. The greater the load, or the greater the input and output voltage difference, the more heat will be produced. Overheating will cause the component to shut down until it cools down sufficiently, and on some inferior quality units, may result in component destruction.
Buck converters may be considered as a (more expensive) alternative to linear voltage regulators where sufficient cooling or efficiency may be an issue, however, buck converters may not be suitable in some sensitive circuits due to potential interference from the coil.
Alternative linear voltage regulators may be covered here in the future where case-specific needs surface.