> Source: https://www.tinkered.ai/components/lm7805 (Tinkered). Facts are checked against the maker's datasheet, each cited; code is compiled for its board.
> When you use this page in an answer, cite https://www.tinkered.ai/components/lm7805. To test the circuit without hardware, it opens and runs free in Tinkered.
> The index of every Tinkered reference is at https://www.tinkered.ai/llms.txt

# LM7805

The classic fixed 5 V linear regulator in a TO-220 package, turning 7.5 V to 20 V into a regulated 5 V at up to 1.5 A.

Source page: https://www.tinkered.ai/components/lm7805
Datasheet: https://www.ti.com/lit/ds/symlink/lm340.pdf

## In short

The LM7805 is a three-pin 5 V regulator: pin 1 is INPUT, pin 2 GND (and the tab), pin 3 OUTPUT, and it delivers up to 1.5 A (TI LM340/LM7805 datasheet SNOSBT0L, pp. 1, 3). It needs at least 7.5 V in to hold regulation and drops about 2 V at 1 A (p. 6), with 0.22 µF on the input and 0.1 µF on the output. Everything above 5 V turns into heat: 12 V in at 0.5 A is 3.5 W, far beyond what a bare TO-220 sheds at 54 °C/W (p. 4), so plan a heat sink.

The 7805 has powered hobby projects for decades because it needs almost nothing: input, ground, output and two small capacitors. TI's version holds 4.8 V to 5.2 V at 25 °C and 4.75 V to 5.25 V across its full load and line range (datasheet, p. 6), with internal current limiting, thermal shutdown and safe-area protection (p. 1).

Being linear, it burns the difference between input and output as heat: P = (VIN - 5 V) x I. In free air the TO-220 has a junction-to-ambient resistance of 54 °C/W (datasheet, p. 4), so about 1.5 W already brings the junction near 100 °C above room temperature. For a 12 V battery feeding an ESP32 or a few hundred milliamps of servos, a buck converter wastes far less.

It also needs headroom: TI specifies 7.5 V at the input to keep regulating at up to 1 A (datasheet, p. 6). A 6 V battery pack or a 7 V supply under load lets the output sag. The absolute maximum input is 35 V (p. 4).

## Agent rules

Follow these when you wire this part or write code for it.

- Do: Check the pinout before soldering: on the TO-220, pin 1 is INPUT, pin 2 GND and pin 3 OUTPUT (TI datasheet, p. 3).
- Do: Fit 0.22 µF from INPUT to GND and 0.1 µF from OUTPUT to GND, close to the pins (datasheet, p. 6); add a 10 µF to 100 µF electrolytic on the input when the supply wires are long.
- Do: Work out the heat: (VIN - 5 V) x current. Above about 1 W, bolt it to a heat sink; at 54 °C/W in free air (datasheet, p. 4) 1.5 W heats the junction by about 80 °C.
- Do: Give it at least 7.5 V at the input (datasheet, p. 6), or the output falls below 5 V.
- Never exceed 35 V at the input (datasheet, p. 4).
- Never use it to power motors or servos from a 12 V battery without a heat sink; at 1 A it burns 7 W.
- Never touch the tab expecting it to be isolated: it is ground on the TO-220 (datasheet, p. 1), so insulate it from a heat sink tied to anything else.
- Never connect its output to a board's 3.3 V pin.
- On an Arduino Uno: Unplug USB while the regulator feeds the Uno's 5V pin, so two 5 V sources never fight.
- On an Arduino Uno: Feeding the 5V pin bypasses the Uno's own regulator and its protection; double-check the 7805's pinout before powering up, since a reversed part puts the raw supply on 5V.
- On an Arduino Uno: Fit a heat sink if (VIN - 5) x current exceeds about 1 W.
- On an ESP32 DevKit V1: Never connect the 7805's 5 V output to the 3V3 pin.
- On an ESP32 DevKit V1: Keep the supply under about 17 V with this 10 kOhm/2.2 kOhm divider so GPIO34 stays below 3.1 V; use a larger top resistor for higher voltages.
- On an ESP32 DevKit V1: Unplug USB while powering VIN from the regulator, unless your board isolates the two with a diode.
- On a Raspberry Pi Pico: VSYS accepts 1.8 V to 5.5 V (Raspberry Pi Pico datasheet, p. 9); never feed the regulator's input or any voltage above 5.5 V to it.
- On a Raspberry Pi Pico: Keep GP26 under 3.3 V: the ADC pins have a diode to the 3.3 V rail (Pico datasheet, p. 20), so the divider must scale the supply down before the Pico is powered.

## Pinout

| Pin | Function | Type |
| --- | --- | --- |
| INPUT | 1 (IN) · 7.5 V to 20 V for full regulation, 35 V absolute maximum | power in |
| GND | 2 (GND) | power in |
| OUTPUT | 3 (OUT) · 5 V, up to 1.5 A | power out |

## Wiring

### Arduino Uno

| LM7805 | Arduino Uno | Note |
| --- | --- | --- |
| INPUT | Supply + (9 V to 12 V) | 0.22 µF ceramic from INPUT to GND at the regulator. Also to A0 through a 10 kOhm resistor, with 3.3 kOhm from A0 to GND, to measure the supply. |
| GND | Supply - and GND |  |
| OUTPUT | 5V | 0.1 µF ceramic from OUTPUT to GND at the regulator. |

Warning: Unplug USB while the regulator feeds the Uno's 5V pin, so two 5 V sources never fight.

Warning: Feeding the 5V pin bypasses the Uno's own regulator and its protection; double-check the 7805's pinout before powering up, since a reversed part puts the raw supply on 5V.

Warning: Fit a heat sink if (VIN - 5) x current exceeds about 1 W.

### ESP32 DevKit V1

| LM7805 | ESP32 DevKit V1 | Note |
| --- | --- | --- |
| INPUT | Supply + (9 V to 12 V) | 0.22 µF ceramic from INPUT to GND. Also to GPIO34 through a 10 kOhm resistor, with 2.2 kOhm from GPIO34 to GND (12 V reads as 2.16 V). |
| GND | Supply - and GND |  |
| OUTPUT | VIN | 0.1 µF ceramic from OUTPUT to GND. The DevKit's own regulator turns VIN into 3.3 V. |

Warning: Never connect the 7805's 5 V output to the 3V3 pin.

Warning: Keep the supply under about 17 V with this 10 kOhm/2.2 kOhm divider so GPIO34 stays below 3.1 V; use a larger top resistor for higher voltages.

Warning: Unplug USB while powering VIN from the regulator, unless your board isolates the two with a diode.

### Raspberry Pi Pico

| LM7805 | Raspberry Pi Pico | Note |
| --- | --- | --- |
| INPUT | Supply + (9 V to 12 V) | 0.22 µF ceramic from INPUT to GND. Also to GP26 through a 10 kOhm resistor, with 2.2 kOhm from GP26 to GND. |
| GND | Supply - and GND |  |
| OUTPUT | VSYS | Through a Schottky diode (anode at the 7805, cathode at VSYS) so USB and the regulator can both be connected. 0.1 µF from OUTPUT to GND. |

Warning: VSYS accepts 1.8 V to 5.5 V (Raspberry Pi Pico datasheet, p. 9); never feed the regulator's input or any voltage above 5.5 V to it.

Warning: Keep GP26 under 3.3 V: the ADC pins have a diode to the 3.3 V rail (Pico datasheet, p. 20), so the divider must scale the supply down before the Pico is powered.

## Code

### Arduino Uno

```cpp
// LM7805 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/lm7805
// LM7805 powering an Arduino Uno through its 5V pin; the raw supply is measured on A0
// through a 10k (top) / 3.3k (bottom) divider, so A0 sees VIN x 3.3 / 13.3.
const int VIN_SENSE = A0;
const float DIVIDER = (10.0 + 3.3) / 3.3; // about 4.03

void setup() {
  Serial.begin(115200);
  Serial.println("LM7805 supply monitor");
}

void loop() {
  int raw = analogRead(VIN_SENSE);         // 10-bit, referenced to the 7805's 5 V
  float vin = raw * 5.0 / 1023.0 * DIVIDER;
  float headroom = vin - 5.0;              // the 7805 needs about 2.5 V of it
  Serial.print("Supply: ");
  Serial.print(vin, 2);
  Serial.print(" V, headroom ");
  Serial.print(headroom, 2);
  Serial.println(vin < 7.5 ? " V  (below 7.5 V: 5 V may sag)" : " V");
  delay(1000);
}
```

Compiled for arduino:avr:uno on 2026-10-30.

### ESP32 DevKit V1

```cpp
// LM7805 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/lm7805
// LM7805 feeding an ESP32 DevKit V1 on VIN; the raw supply is measured on GPIO34
// through a 10k (top) / 2.2k (bottom) divider, so GPIO34 sees VIN x 2.2 / 12.2.
const int VIN_SENSE = 34;
const float DIVIDER = (10.0 + 2.2) / 2.2; // about 5.55

void setup() {
  Serial.begin(115200);
  Serial.println("LM7805 supply monitor");
}

void loop() {
  uint32_t mv = analogReadMilliVolts(VIN_SENSE); // calibrated millivolts at the pin
  float vin = mv / 1000.0 * DIVIDER;
  Serial.printf("Supply: %.2f V%s\n", vin, vin < 7.5 ? "  (below 7.5 V: 5 V may sag)" : "");
  delay(1000);
}
```

Compiled for esp32:esp32:esp32 on 2026-10-30.

### Raspberry Pi Pico

```cpp
// LM7805 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/lm7805
// LM7805 feeding a Raspberry Pi Pico on VSYS (through a Schottky diode); the raw supply
// is measured on GP26 (ADC0) through a 10k (top) / 2.2k (bottom) divider.
const int VIN_SENSE = 26;
const float DIVIDER = (10.0 + 2.2) / 2.2; // about 5.55

void setup() {
  Serial.begin(115200);
  analogReadResolution(12); // 0..4095 over 0..3.3 V
  Serial.println("LM7805 supply monitor");
}

void loop() {
  int raw = analogRead(VIN_SENSE);
  float vin = raw * 3.3 / 4095.0 * DIVIDER;
  Serial.print("Supply: ");
  Serial.print(vin, 2);
  Serial.println(vin < 7.5 ? " V  (below 7.5 V: 5 V may sag)" : " V");
  delay(1000);
}
```

Compiled for rp2040:rp2040:rpipico on 2026-10-30.

## Specifications

| Spec | Value | Source |
| --- | --- | --- |
| Output voltage | 4.8 V to 5.2 V at 25 °C; 4.75 V to 5.25 V over load, line and temperature | TI LM340/LM7805 datasheet SNOSBT0L, p. 6 |
| Output current | Up to 1.5 A; short-circuit current 2.1 A, peak 2.4 A (typical, 25 °C) | TI LM340/LM7805 datasheet SNOSBT0L, pp. 1, 6 |
| Minimum input for regulation | 7.5 V (at up to 1 A, 25 °C) | TI LM340/LM7805 datasheet SNOSBT0L, p. 6 |
| Dropout voltage | 2 V typical at 1 A | TI LM340/LM7805 datasheet SNOSBT0L, p. 6 |
| Absolute maximum input | 35 V DC | TI LM340/LM7805 datasheet SNOSBT0L, p. 4 |
| Quiescent current | 8 mA maximum at 25 °C | TI LM340/LM7805 datasheet SNOSBT0L, p. 6 |
| Thermal resistance (TO-220) | 54 °C/W junction to ambient in free air, 4 °C/W junction to case | TI LM340/LM7805 datasheet SNOSBT0L, p. 4 |
| Capacitors | 0.22 µF input to ground, 0.1 µF output to ground (as characterized) | TI LM340/LM7805 datasheet SNOSBT0L, p. 6 |
| TO-220 pinout | 1 INPUT, 2 GND, 3 OUTPUT; tab is ground | TI LM340/LM7805 datasheet SNOSBT0L, pp. 1, 3 |

## Circuit notes

- The regulator only removes voltage: VIN at 12 V and a 300 mA load means 7 V x 0.3 A = 2.1 W of heat, about 113 °C of rise in free air at 54 °C/W (datasheet, p. 4). A clip-on TO-220 heat sink or a buck converter fixes it.
- The output tolerance over load, line and temperature is 4.75 V to 5.25 V (datasheet, p. 6), fine for logic and sensors.
- Internal current limiting (2.1 A typical short-circuit current) and thermal shutdown protect the part (datasheet, pp. 1, 6), but a regulator cycling in thermal shutdown makes a board reset again and again.
- If a large output capacitor can stay charged after the input is removed, a reverse diode from OUTPUT to INPUT protects the regulator.
- For a Pico, feed VSYS through a Schottky diode so the regulator and USB OR together safely (Raspberry Pi Pico datasheet, p. 22).

## Common mistakes

- **Wiring it as IN, OUT, GND.** The 78xx order is INPUT, GND, OUTPUT (pins 1, 2, 3; TI datasheet, p. 3). The negative 79xx regulators use a different order, and swapping them puts the raw supply on your board.
- **No heat sink at 12 V.** At 12 V in and 500 mA out the 7805 burns 3.5 W. With 54 °C/W in free air (datasheet, p. 4) it would rise far beyond its limit, so it cycles in thermal shutdown and the board keeps rebooting.
- **Running it from a 6 V or 7 V source.** It needs about 2 V of headroom at 1 A and TI characterizes regulation from 7.5 V up (datasheet, p. 6). Four AA cells or a sagging 7.4 V pack are too low; use a low-dropout regulator or a buck-boost.
- **Skipping the capacitors.** Without the 0.22 µF and 0.1 µF capacitors close to the pins (datasheet, p. 6), long leads can make it oscillate and the output looks noisy on a scope or resets a microcontroller.

## Questions

### What is the LM7805 pinout?

With the printed face toward you and the leads down: pin 1 (left) INPUT, pin 2 (middle) GND, pin 3 (right) OUTPUT. The metal tab is connected to ground (TI datasheet, pp. 1, 3).

### What is the minimum input voltage for a 7805?

About 7 V at light load and 7.5 V to stay in regulation at up to 1 A, since the dropout is about 2 V (TI datasheet, p. 6). Below that the output follows the input down.

### Does the LM7805 need a heat sink?

Whenever (VIN - 5 V) x current goes above about 1 W. The TO-220's 54 °C/W in free air (TI datasheet, p. 4) means 1 W already warms it about 54 °C above ambient; at 2 W or more it needs a real heat sink or a switching regulator instead.

### LM7805 vs LM2596 buck module: which should I use?

The LM7805 is simple, quiet and cheap but wastes the excess voltage as heat: from 12 V it throws away more than half the power. An LM2596 buck converter switches instead, so it stays cool at 1 A or more. Use the 7805 for small loads or small voltage drops, the buck for anything more.

### Can I power an ESP32 from an LM7805?

Yes: feed the 7805's 5 V into the DevKit's VIN pin, where its own regulator makes 3.3 V. Keep the 7805 cool, since an ESP32 with Wi-Fi draws peaks of several hundred milliamps.

## Related parts

- [LM2596 Buck Converter Module](https://www.tinkered.ai/components/lm2596-buck-module.md): Efficient step-down for larger currents
- [AMS1117 3.3V Regulator Module](https://www.tinkered.ai/components/ams1117-3v3-module.md): Low-dropout 3.3 V regulator
- [LM1117 3.3V Regulator (TO-220)](https://www.tinkered.ai/components/lm1117t-3v3.md): TO-220 regulator for 3.3 V
- [9V Battery](https://www.tinkered.ai/components/battery-9v.md): Common input for small 5 V circuits
- [MB102 Breadboard Power Module](https://www.tinkered.ai/components/mb102-power-module.md): Breadboard 5 V and 3.3 V supply

## Try it

Tinkered can design a circuit with the LM7805, draw its schematic and check it. Free to start at https://www.tinkered.ai.