# LM7805 regulator: fixed 5 V, up to 1.5 A, 2 V dropout

> The classic fixed 5 V linear regulator: current, input range, dropout, protection and the heat it makes from a 12 V battery.

Canonical: https://roboticsengineering.in/components/lm7805-fixed-regulator/ | Published: 2026-11-03 | Updated: 2026-11-03

**The LM7805 is a three-terminal fixed 5 V linear regulator that can deliver over 1.5 A with adequate heat sinking, has internal current limiting, thermal shutdown and safe-area protection, and needs no output capacitor to stay stable.** It is the simplest way to make 5 V from a 7.5 to 20 V battery, and a common source of heat in beginner robots. Figures are from the Texas Instruments LM340 and LM7805 family datasheet SNOSBT0L.

## Key specifications

| Output | fixed 5 V (also 12 V, 15 V in family) |
| --- | --- |
| Current | up to 1.5 A with heat sinking |
| Dropout | 2 V at 1 A |
| Input (spec range) | 7.5–20 V |
| Absolute max input | 35 V |
| Protection | current limit, thermal, SOA |

## What the datasheet promises

| Item | Datasheet value |
| --- | --- |
| Output current | Up to 1.5 A with adequate heat sinking |
| Fixed outputs | 5 V, 12 V and 15 V options in the family |
| Output tolerance | ±2 percent at 25 °C for the LM340A |
| Line regulation | 0.01 percent per volt at a 1 A load (LM340A) |
| Load regulation | 0.3 percent per amp (LM340A) |
| Dropout voltage | 2 V at 1 A, 25 °C (LM7805) |
| Input voltage (5 V part) | Electrical characteristics are specified for 7.5 to 20 V in; the absolute maximum DC input is 35 V |
| Ripple rejection | 68 dB (8 to 18 V input) |
| Protection | Internal thermal overload, short-circuit and safe-area protection |
| Capacitors | Output capacitance is not required for stability; input bypassing is needed only if far from the supply filter capacitor |
| Packages | SOT-223 and others |

The datasheet describes the family as essentially indestructible because of its protection circuits. That means it survives abuse by shutting down, not that it will stay cool: heat is the voltage drop times the current.

## The heat problem

From a 12 V battery to 5 V at 500 mA, the regulator drops 7 V and dissipates 3.5 W, which is far more than a bare TO-220 can lose to air, so it needs a heatsink. A buck converter such as the [LM2576](https://roboticsengineering.in/components/lm2576-buck-regulator/) or the [LM2596](https://roboticsengineering.in/components/lm2596-buck-converter/) wastes much less. For lower voltage rails, see the [LM1117](https://roboticsengineering.in/components/lm1117-ldo-regulator/). The 3.5 W is a calculation, not a measurement.

## Sources and further reading

- [Texas Instruments LM340, LM340A and LM7805 family datasheet (SNOSBT0L)](https://www.ti.com/lit/ds/symlink/lm340.pdf) — the current, regulation, dropout, input range and protection above.

Last reviewed: November 2026. Limits are from the Texas Instruments datasheet; regulators from other makers differ. No price is quoted because it has not been checked.