dropoutspænding

Dropoutspænding, commonly referred to as dropout voltage, is the minimum difference between the input voltage and the output voltage required for a linear voltage regulator to maintain regulation. When the input voltage drops below the sum of the desired output voltage and the dropout voltage, the regulator can no longer produce a stable output and the output voltage collapses toward the input level.

The value of dropout voltage depends on the type of regulator. LDO (low‑dropout) regulators typically have dropout voltages as low as a few tens of millivolts, making them suitable for battery‑powered devices where the input and output voltages are close. Classic linear regulators used in older designs may require dropout voltages of up to a volt or more. Switching regulators generally have higher dropout voltages due to the active components and dead‑time required for switching operation, but modern synchronous buck converters can achieve dropout voltages below 1 V even at higher output currents.

Dropout voltage is specified in datasheets and is a critical design parameter when selecting a regulator for a given application. It influences the minimum supply voltage, power efficiency, and the ability to meet load regulation requirements. Engineers calculate the required input voltage by adding the desired output voltage to the dropout voltage, plus a safety margin to account for component tolerances and temperature variations.

In practice, dropoutvoltage considerations affect a wide range of electronics, from microcontroller power supplies and sensor interfaces to automotive power distribution. Understanding the dropout characteristics of a regulator allows designers to size power supplies appropriately, ensure reliable operation, and optimize overall system performance.