Common types of diodes to keep around

Question

I'm working on stocking my home workshop with frequently used parts so I can spend more time tinkering and less time watching my mailbox.

What are the differences between different kinds of diodes? I've seen schottky, zenner, signal, and rectifier all used to describe diodes, but I don't know what the differences are and when you would use a particular one.

What are the most frequently used diodes that you would keep around to be able to build most common circuits? And how do you know what makes a suitable substitute when a circuit calls for a particular diode?

Answer 1

1N4148 and 1N400x(*). Definitely.

The 1N4148 is the standard signal diode, the 1N4001 a rectifier capable of 1 A and 50 V. If you need higher voltages you can go for the 1N4002 through 1N4007, for 100 V and 1000 V respectively. See also this answer.

Zeners. You don't want zeners. :-) Well, you could keep a few, but what voltage(s)? Most often you'll use a three-legged regulator, like an LE33, for instance. They regulate much better than zeners. Unless! (and this should please Russell) There's always the TL431, which is an adjustable zener, and because it has an adjustable voltage you only need one type. Costs hardly more than a zener, but has much better specs.

(*) I first mentioned the 1N4001 here, but on second thought the 1N4007 may be a better choice: you can use that for almost any application, including rectifying 230 V AC, like Olin says. Not what I would need everyday, but the 1N4007 is exactly the same price as the 1N4001 at Digikey anyway (6.49 ¢ a piece @ 100s), and the 1N4007 has a lower junction capacitance as well.

Answer 2

What are the differences between different kinds of diodes?

Shottky diodes are formed by a metal-semiconductor junction instead of a junction between two differently-doped semiconductor regions. As Olin says in his answer, they have lower forward voltage drop and generally faster reverse recovery characteristics. They're often used in switching power supplies to minimize losses.

Zener diodes are silicon-junction diodes that are designed to have well-controlled reverse-breakdown characteristics. When reverse-biased with a low voltage they will conduct only minute currents, like normal diodes. But when reverse-biased beyond their reverse breakdown voltage they will conduct strongly. Normal diodes also have reverse breakdown behavior, but the Zener diode is designed to break down at a well-controlled voltage. The breakdown voltage can range from 1 or 2 V up to 50 V or more. They are often used as shunt voltage regulators or in input protection circuits.

Rectifier and small-signal diodes are just normal silicon diodes, but optimized or specified for two different applications. Rectifiers are used to block current in one direction, for example in a bridge circuit to convert AC to DC. Small-signal diodes do the same, but for smaller currents and often at higher frequencies. These diodes are optimized for low capacitance and sharp turn-on instead of current carrying ability.

You might also add varactor diodes (used for their variable capacitance when reverse biased), p-i-n diodes (often used as rf and optical detectors), LEDs, and laser diodes to your list of diode types to be aware of.

Answer 3

I agree with Steven about the 1N4148. That's a very common fast signal diode.

However, I would get 1N4004 instead of 1N4001. These are both common 1 A silicon power rectifiers, but the 1N4004 has a higher voltage rating. There is very little benefit to using the 1N4001 in low enough voltage applications instead of a 1N4004, but the 1N4004 allows for power line applications that the 1N4001 doesn't.

I know of at least one case where a manufacturer actually made a single type of diode for a class of different products rated for different voltages. They would send them unlabeled to distributors, who would then label them appropriately according to what voltage rating the customer paid for. All diodes were actually identical, but the lower voltage rating sold for less money. I wouldn't be too surprised to find that many 1N4001 and 1N4004 from a single manufacturer are actually the same diode with different markings.

In addition to these two, I'd also get some 40 V 1 A Schottky diodes. Schottkys have two main advantages over silicon diodes in low voltage applications. First, they have about half the forward drop. Second, they have instant reverse recovery times for most purposes, which full silicon rectifier diodes certainly don't have. This can be very important in switching applications. I don't have specific model numbers, so look around on Mouser and see what is available. The SMA package is convenient for the 1 A current range.

Answer 4

I would like to prefer two diodes for your own home amateur or professional lab.

Diode 1N4148 is highly recommended for high speed communications, This has 4nS switching time, which is very very fast, it is ideal for communication purpose as well as low voltage and current AC to DC rectification. Its maximum rated current is low as compared to 1N404x series.

Small General purpose Diode 1N4007 is highly recommended for lab general purpose, however you may use from 1N4001 to 1N4007 diodes, all these diodes have rated current upto 1A, the only difference between them is of maximum voltage ratings, I personaly recommend 1N4007 diode, which is best among 1N400x series, due to its maximum voltage level which is 1000 volts. all diodes from 1N4001 to 1N4007 comes with almost similar price.

1N4001: 50V

1N4002: 100V

1N4003: 200V

1N4004: 400V

1N4005: 600V

1N4006: 800V

1N4007: 1000V

3.6V zener diode is recommended, if your dealing with USB communication projects.

5.1V zener diode is recommended for general purpose use. It can be useful to produce 5.1V supply, as well as for reference voltage supply, It can be used in communication project where micro-controller pins are directly connected to external boards for keeping communication line voltage levels in between minimum and maximum voltage levels of micro-controllers (for this use connect cathode of zener diode to micro-controller pin and connect anode pin to common ground of micro-controller board)

Answer 5

Similar to you, I bought many components so I wouldn't have to spend much time watching the mailbox. Some of my experience:

While the 1N4148 has its uses, a 1N4007 will work just as well in many circuits (at least simple ones), even if it's not always the best choice. But considering the 1N4148 costs about 2 cents if not less, sure, get some.

Like the other responders here, I see little value in the 1N4001-1N4006. Get the 1N4007, it's often about 2 cents.

Schottky diodes, yes. But skip the 20V ones like the 1N5817. While their forward voltage is extremely low, in my experience they leak some current in the "wrong" direction, even in <10V circuits. So get Schottky diodes that are rated for at least 40V like the 1N5819.

Depending on what you plan to make, some higher current diodes could come in handy as well. As the current goes up the forward voltage will also go up a little, so having some headroom can be beneficial. Other than that, they can be used to protect MOSFETs. Some (many? most?) MOSFETs have an internal diode to protect it, but this internal diode is very small and can be damaged by large currents, turning the internal diode into a conductor and turning the MOSFET into e-waste. A larger external Schottky diode in parallel with the internal diode is recommended in this case.

I actually disagree with the majority here on Zener diodes. I've used them in three scenarios. When I needed a VRM that could handle an input of more than 30V, I used one NPN transistor that was rated for a high voltage (I used an MPSA 42, IIRC), a resistor and a Zener diode. Connect the input to the transistor collector and resistor, the other side of the resistor to the transistor base and run the Zener diode between the transistor base and ground. It's not super precise, but if needed you can use a second VRM (either the same kind or something off-the-shelf) in conjunction with this.

Another scenario is to protect some components. 18V Zener diodes can be used to protect the gate of most N-channel MOSFETs (which is typically rated for 20V max) by connecting it between the gate and drain. Something similar goes for most components with a breakdown voltage. A TVS diode would be better suited for this purpose but may be relatively expensive depending on where you shop.

The third scenario is to simply use Zener diodes as regular diodes. Zener diodes are designed to also function in reverse without instantly breaking whereas other diodes are almost instantly irreversibly damaged when their breakdown voltage is exceeded. In some applications this might be an advantage.

One final note: if you occasionally modify or repair existing devices, consider buying SMD variants of these diodes, either in addition to or instead of through-hole components, depending on your soldering skills. I frequently find myself running out of space when working on some existing device and SMD components can be the answer in that case. They also tend to be cheaper. For example SS14 (similar to 1N5819), SS34 (same but 3A), M7 (similar to 1N4007), LL4148 (similar to 1N4148). For Zener diodes, search for "LL34 Zener". Just beware that LL34/MELF is called a "roll-away package" for a reason and that MELF actually stands for Most End up Lying on the Floor. There are also Zener diodes using other packages (SOT-23 or DO-214 for example) but LL34 is often cheaper and easier to find.