Linear / LDO
LM7805
Fixed 5V linear regulator, TO-220 — 1.5A rated, but heat is the real ceiling, not current.
LM7805 · onsemi (also TI, STMicroelectronics and others — a standard multi-sourced part)
Overview
The regulator everyone's first breadboard project used: three legs, feed it 7-35V, get a steady 5V out, up to 1.5A on paper. The number that actually limits it in practice is thermal, not electrical. Dropping 12V to 5V at 500mA dissipates (12V-5V)×0.5A = 3.5W as heat in the regulator alone — and the TO-220 package's junction-to-ambient thermal resistance with no heatsink is about 65°C/W, so that 3.5W alone would try to push the junction over 200°C above ambient. Long before that the chip hits thermal shutdown and starts cycling on and off rather than holding 5V steady. Anything drawing real current from a meaningfully higher input voltage needs a heatsink, or — better, for anything approaching even a few hundred mA at a large Vin-Vout gap — a switching buck regulator instead, which wastes a fraction of the power as heat for the same job. At small voltage drops and light loads (say, 9V to 5V at 100mA, under 0.5W) it runs perfectly cool with no heatsink at all.
Wiring tip: VIN → 7V+ rail, GND → GND (and the metal tab), VOUT → 5V rail — add a heatsink above a watt or so
Pins & wiring
LM7805
TO-220
Physical pin order shown left to right.
All pins
Hover · click to selectSelected pin
VIN
- Direction
- Power
Full pin table
| Pin | Name | Role | Direction | Note |
|---|---|---|---|---|
| 1 | Power | Power | — | |
| 2 | Ground | Passive | Also the metal tab on the back of the package — tab is GND, not a floating heatsink pad, so mounting a metal heatsink directly on it ties the heatsink to GND. | |
| 3 | Power | Out | — |
Wiring examples
9-12V wall adapter down to a breadboard 5V rail
Any 5V hostThe textbook application circuit: input and output bypass caps, a common-ground 5V rail out.
| LM7805 pin | Connects to | Note |
|---|---|---|
| VOUT | 5V | — |
| GND | GND | — |
You also need
- Required330 nF capacitor between VIN and GND — 0.33µF input bypass, required if the regulator sits more than a few inches from the main input filter capacitor — standard 78xx app-note value.
- Optional100 nF capacitor between VOUT and GND — 0.1µF output bypass improves transient response — standard 78xx app-note value, not strictly required for stability like the AMS1117's larger output cap is.
- Run the heat math for your actual Vin and Iout before skipping a heatsink: (Vin-5V) × Iout in watts, and remember the bare TO-220 package is ~65°C/W to ambient. Even a modest 1W will run the case uncomfortably hot to the touch.
- The metal tab is electrically GND. A bolt-on heatsink is fine; touching the tab to anything else on the board is a short.
Specifications
Footprint
No independently verified physical footprint is on file for this part yet.
Alternatives
Upgrades
Strictly better on the headline spec, but expect to touch firmware or wiring to actually use the difference.
Dropping more than a couple volts at real current — the heat math above gets ugly fast on a linear part. A switching buck does the same job at a fraction of the wasted power.
Compare with LM7805- Topology: linear → switching (buck) — Trades away the LM7805's simplicity (no inductor, no trimpot) for real efficiency at a meaningful Vin-Vout gap.
Similar parts
Does the same job with a different part. Expect wiring and library changes — a starting point, not a guarantee.
Same linear-regulator dropout tradeoff in a much smaller SOT-223 package, fixed at 3.3V instead of 5V — pick it when the downstream load is 3.3V logic, not 5V.
Compare with LM7805- Output voltage: 5V → 3.3V
- Max output current: 1.5A → 1A
Documents
Datasheets
Frequently asked questions
What voltage does the LM7805 run at?
The LM7805 runs at 5V, per the spec sheet below. Always double-check against the specific board you have — some breakouts add an onboard regulator that changes the usable input range.
How many pins does the LM7805 have?
The LM7805 has 3 pins. See the full pinout table in Pins & wiring for each pin's role.
Can I simulate the LM7805 before ordering hardware?
Not yet — the LM7805 does not have a live simulation model in Banana Board today, so validate the wiring here and test on real hardware.
Where is the LM7805 datasheet?
Linked in the Documents section on this page, and cited on every spec that came from it.
Related references
Build it, do not just look it up
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