Metal tab (heat sink) · Ø 3.7 mm holeEpoxy bodyPins IN-GND-OUT · 2.54 mm spacing

Black TO-220 body, metal tab with a hole, “L7805CV” text, three legs
TO-220 body ≈ 10 × 15 mm, metal tab with a hole

Integrated circuits

Voltage regulator (7805)

In simple terms

What is this?

A pressure reducer that turns excess voltage into heat and throws it away; the pressure at the output always stays at the same level.

What is it for?

It produces a steady five volts from a high-voltage adapter or battery; the microcontroller can work safely.

Where do you see it?

In old adapters, chargers and breadboard power modules.

How do you spot it?

Small black body with a metal tab and three pins: input, ground and output.

Caution:

Don't connect input and output in reverse; at high current and a large voltage difference it gets very hot and needs a heatsink.

Technical definition

A linear regulator that drops a higher voltage applied to its input down to a fixed 5 V. Because the voltage difference turns into heat, a heatsink is needed at high current and large voltage differences. It has internal protection against short circuits and overheating.

Output5 V

Current≤ 1 A

Input7–35 V

Schematic symbol Same in IEC and ANSI

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 3

1IN (input)With the marked face toward you, legs at the bottom, 1 from the left.; at least ≈7 VIN

2GNDMiddle leg; the metal tab is also connected to GNDGND

3OUT (output)Right leg; fixed 5 VOUT

Features typical

Output voltage: 5 V (4.8–5.2 V)
Input: 7–35 V (≈2 V drop)
Max. current: ≈1 A (with heatsink)
Capacitors: Input 0.33 µF · output 0.1 µF
Heat: P = (Vin − 5 V) × I
Example: 12 V, 0.5 A → 3.5 W heat
Protection: Short circuit and thermal shutdown
Example part: L7805CV (TO-220)

Common mistakes

Forgetting the heatsinkIf you draw 500 mA from 12 V, the regulator makes 3.5 W of heat; a TO-220 without a heatsink overheats and shuts itself down.

Mixing up pinsThe order is IN, GND, OUT (from the left, with the text facing you). 79xx negative regulators have a different order.

Driving it with a low inputThe input must be at least ≈7 V. 4 AA batteries (6 V) cannot give a stable 5 V for the 7805.

Test with a multimeter

Test whether this part is good with the multimeter on the measurement screen.

Take a measurement

Where it is used

5 V from a 9–12 V adapterMicrocontroller power supplyBreadboard power moduleShort experiments with a 9 V battery

Try it in the Lab