Skip to content
LearnEE
Sign inGet started

Reference chart

Common diodes chart

Print it: Circuit symbols cheat sheet (PDF: A4 · US Letter)

Most hobby circuits use the same handful of diodes. This chart gives each one's ratings from its datasheet, how much voltage it drops, and the jobs it's good for, so you can pick the right one from the drawer.

The everyday diodes

PartTypeMax reverse voltageMax current
1N4148Small-signal silicon75 V (100 V peak)150–200 mA, by maker
1N4001–1N4007Silicon rectifier50–1000 V (table below)1 A
1N5817Schottky20 V1 A
1N5818Schottky30 V1 A
1N5819Schottky40 V1 A
1N5822Schottky40 V3 A

The current is the average forward current. Short surges can be much higher. Ratings vary a little between makers, so check the datasheet for your exact part.

Forward drop and what each is for

PartForward drop (datasheet maximum)Use it for
1N41481 V at 10 mASignals and logic, fast switching, protecting chip inputs
1N4001–1N40071.1 V at 1 ARectifiers, reverse-polarity protection, flyback diodes on relays and motors
1N58170.45 V at 1 ALow-loss polarity protection on 5 V and 12 V
1N58180.55 V at 1 AThe same, with more voltage margin
1N58190.6 V at 1 AThe same, up to 24 V, and switching regulators
1N5822about 0.5 V at 3 ABigger loads, like motors and LED strips

These are worst-case figures at full current. At a few milliamps a silicon diode drops about 0.6–0.7 V and a Schottky about 0.2–0.3 V, the rules of thumb the lessons use.

The 1N400x family

All seven pass 1 A and differ only in the reverse voltage they block:

PartMax reverse voltagePartMax reverse voltage
1N400150 V1N4005600 V
1N4002100 V1N4006800 V
1N4003200 V1N40071000 V
1N4004400 V

1N47xx Zener diodes

The 1N47xx series are 1 W Zeners. The A at the end means a ±5% tolerance on the Zener voltage.

PartZener voltagePartZener voltage
1N4728A3.3 V1N4739A9.1 V
1N4729A3.6 V1N4740A10 V
1N4730A3.9 V1N4741A11 V
1N4731A4.3 V1N4742A12 V
1N4732A4.7 V1N4743A13 V
1N4733A5.1 V1N4744A15 V
1N4734A5.6 V1N4745A16 V
1N4735A6.2 V1N4746A18 V
1N4736A6.8 V1N4747A20 V
1N4737A7.5 V1N4748A22 V
1N4738A8.2 V1N4749A24 V

Smaller 0.5 W Zeners, like the BZX79 series, are named by their voltage instead: a BZX79-C5V1 is 5.1 V, with V for the decimal point. The most current a Zener can take is its power rating ÷ VZ.

Picking a diode

  1. Reverse voltage: pick a part rated well above the highest voltage it will block, ideally twice.
  2. Current: pick one rated above your load current, with room to spare.
  3. Drop: if every tenth of a volt counts, use a Schottky. If the voltage is high, use silicon.
  4. Speed: for signals and logic, use a 1N4148.

Free lesson

Now build it yourself

Each lesson comes in three short parts: see the idea, try it on a live board, then build it yourself, with quick checks as you go.

Try it yourself: free lesson

“Diodes” is lesson 1 of 6 in Silicon Ridge, Electronics World 5. Free with an account. Lessons unlock in order, so you’ll do the 28 before it first.

Or start from the very first lesson, no account needed

Work it out

The ideas behind it

Questions people ask

What's the difference between a 1N4001 and a 1N4007?

Only the reverse voltage they can block: 50 V for the 1N4001, up to 1000 V for the 1N4007. Both pass 1 A and drop about the same voltage. A 1N4007 works anywhere a 1N4001 does, which is why kits are full of them.

Can I use a 1N4148 instead of a 1N4007?

Only for small currents. A 1N4148 is a signal diode rated for about 150–200 mA and 75 V, where a 1N4007 takes 1 A and 1000 V. The 1N4148 switches much faster, so it's the better choice for signals and logic.

Which end of a diode is the cathode?

The end with the stripe. Current flows from the anode into the cathode. On the circuit symbol, the bar is the cathode. On a Zener in a regulator, the stripe goes toward +.

How much current can a 1N47xx Zener take?

They're rated for 1 W, so the most current is about 1 W ÷ the Zener voltage, around 196 mA for a 5.1 V part. Design for half that or less, because a Zener at full power runs very hot.

More charts