Glass body (DO-35) · Ø 1.85 × 3.8 mmDumet lead (copper-clad)Cathode bandPins

Clear orange glass body, black cathode stripe, thin axial legs
DO-35 glass body ≈ 4 × 1.9 mm

Diodes

Signal diode (1N4148)

In simple terms

What is this?

A small, very fast one-way gate for electricity; made for small currents.

What is it for?

Protects fast signals and logic inputs; it passes a small signal, not a large current.

Where do you see it?

On small electronic boards, in remote controls and in logic circuits.

How do you spot it?

A small glass tube that looks orange-red, with a black strip at one end.

Caution:

The striped end is the cathode; do not pass a large current, a small glass diode gets damaged right away.

Technical definition

A small-current, very fast-switching general-purpose signal diode. Its glass body looks orange-red and its cathode is marked with a black stripe. It is used in logic circuits, pulse shaping and input protection.

Reverse voltage100 V

Current150–200 mA

trr≤ 4 ns

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)Black-striped sideK

Features typical

Max. peak reverse voltage: 100 V
Continuous reverse voltage: 75 V
Forward current: 150–200 mA (depends on manufacturer)
Forward voltage: ≤ 1 V (10 mA)
Reverse recovery: ≤ 4 ns
Capacitance: ≤ 4 pF
Package: DO-35 glass
Example part: 1N4148 (DO-35 glass)

Common mistakes

Using it for power workAbove hundreds of mA it heats up and fails. For a power supply or motor choose 1N4007 or a Schottky.

Not seeing the stripeOn a glass body the stripe is thin and black. Look with a magnifier or check its direction with the multimeter’s diode mode.

Test with a multimeter

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

Take a measurement

Where it is used

Logic input protectionDiode OR gateSignal rectification (peak detector)Flyback for small coils