Rectifier diode (1N4007) · Exterior view
Epoxy body (DO-41) · Ø 2.7 × 5.2 mm1N4007 · 1000 V, 1 ACathode band (gray)Pins (anode / cathode)
Black cylindrical body, silver stripe at one end, “1N4007” text, axial leads
DO-41 body ≈ 5 × 2.7 mm, axial leads
Diodes

Rectifier diode (1N4007)

In simple terms
What is this?

The one-way gate of electricity. Current passes in one direction and cannot return in the reverse direction.

What is it for?

Turns alternating current one way; protects the circuit from a reversed battery and from coil spikes.

Where do you see it?

Small black cylinders inside phone chargers and adapters.

How do you spot it?

A black cylindrical body with a silver strip at one end; the strip is the cathode end.

Caution:

The strip side is the output; if you put it in reversed, no current flows and the circuit does not work.

Technical definition

A general-purpose silicon diode passing current only from anode to cathode. 1N4007 handles 1000 V reverse voltage and 1 A average current. It is slow: use for low-frequency rectification and protection.

Reverse voltage1000 V
Current1 A
Forward voltage≤ 1.1 V
Schematic symbol Same in IEC and ANSI

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

Pins 2
1Anode (A)Unstriped sideA
2Cathode (K)Side with the silver or white stripeK
Features typical
Max. reverse voltage
1000 V
Average forward current
1 A
Surge current
30 A (8.3 ms)
Forward voltage
≤ 1.1 V (1 A)
Reverse leakage
≤ 5 µA (25 °C)
Package
DO-41
Example part
1N4007 (DO-41)
Common mistakes
Fitting it with the stripe the wrong wayThe stripe is the cathode and matches the barred side of the symbol. A diode fitted backwards blocks current.
Forgetting the flyback diodeWhen a relay or motor coil switches off, it produces a high reverse voltage. Connect a 1N4007 in reverse parallel across the coil, with the cathode to plus.
Forgetting the voltage dropAbout 0.7–1 V drops across a conducting diode. From a 5 V input you can't get a full 5 V after the diode.

Test with a multimeter

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

Take a measurement
Where it is used
Bridge rectifierReverse battery protectionRelay and motor flyback diodeSimple voltage reduction
Related lessons
Rectifying with a diode
Module 4 · Diode and transistorsoonDriving a relay and the flyback diode
Module 4 · Diode and transistorsoonDiode test
Module 2 · Measuring with a multimetersoon
Try it in the Lab