Linear Regulators

Regulators like the 7805 and LM317 hold a steady output voltage by burning the excess as heat.

Easy

A linear regulator acts as a variable resistor controlled by feedback. Fixed: 78xx (positive), 79xx (negative), AMS1117-3.3. Adjustable: LM317:

$V_{out} = 1.25\left(1 + \frac{R_2}{R_1}\right)$

(with $R_1$ = 240 Ω typically).

Power wasted:

$P = (V_{in} - V_{out}) \times I_{out}$

12 V → 5 V at 1 A wastes 7 W — it needs a heatsink and is only 42 % efficient. Linear regulators are quiet and simple; use them for small currents or small voltage drops.

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LDO Regulators

Low-dropout regulators keep regulating with only a few hundred millivolts between input and output.

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LDO Regulators

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