page_title: Linear regulator
section_title: Fixed regulators
hierarchical_section_title: Linear regulator / Fixed regulators
caption_attribution_description: English: 78xx regulator ICs
context_page_description: In electronics, a linear regulator is a system used to maintain a steady voltage. The resistance of the regulator varies in accordance with both the input voltage and the load, resulting in a constant voltage output. The regulating device is made to act like a variable resistor, continuously adjusting a voltage divider network to maintain a constant output voltage and continually dissipating the difference between the input and regulated voltages as waste heat. By contrast, a switching regulator uses an active device that switches on and off to maintain an average value of output. Because the regulated voltage of a linear regulator must always be lower than input voltage, efficiency is limited and the input voltage must be high enough to always allow the active device to drop some voltage.
  Linear regulators may place the regulating device in parallel with the load or may place the regulating device between the source and the regulated load. Simple linear regulators may only contain as little as a Zener diode and a series resistor; more complicated regulators include separate stages of voltage reference, error amplifier and power pass element.
context_section_description: "Fixed" three-terminal linear regulators are commonly available to generate fixed voltages of +3.3 V, and plus or minus 5 V, 6 V, 9 V, 12 V, or 15 V, when the load is less than 1.5 A.
  The "78xx" series (7805, 7812, etc.) regulate positive voltages while the "79xx" series (7905, 7912, etc.) regulate negative voltages. Often, the last two digits of the device number are the output voltage (e.g., a 7805 is a +5 V regulator, while a 7915 is a −15 V regulator). There are variants on the 78xx series ICs, such as 78L and 78S, some of which can supply up to 2 A.
caption: An assortment of 78xx series ICs
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