A diode is an electronic component which allows the current to flow through it in one direction but not the other side.

A diode can be used as a rectifier which converts AC voltage to DC voltage in power supply applications. A diode can also be used to filter out radio frequency signals in reciever applications.

Common types of diode:

The photo above shows different kinds of diodes. You can see that it has different packages. The common packages are DO-35, D0-41, TO-220. Diodes has many applications, a high-speed rectifier diode is used mainly in SMPS ( Switched Mode Power Supplies ), they usually have a higher current output rating and high-speed switching capabilities. A signal diode can be used to recieve radio frequency signals like AM (amplitude modulation) signals. These are commonly used in AM radio receivers.

The schematic symbol for a semiconductor diode is shown below.
A stands for ANODE
K stands for CATHODE

  back to top RECTIFIER DIODES

examples of an aluminum electrolytic capacitor
Photo of an MUR460 Ultrafast Recovery Rectifier Diode

schematic symbol for an electrolytic capacitor
Photo of a 1N5408 General Purpose Rectifier Diode

Rectifier diodes have similar appearance with one another, to identify the diode, you should look into its marking carefully before using it.

Rectifier diodes are commonly used in power supply circuit applications. They are used to convert AC voltage into DC voltage.

The CATHODE end of the diode is usually marked with a stripe band. Rectifier diodes are made to handle high currents, however, it is not advisable to use the diodes maximum rating. A 70% - 80% rating is advisable to avoid any component breakdown. Heat is one common factor in a component breakdown. When a component exceeds its maximum temperature capabilities, it could be damaged permanently.

The operating principle of a rectifier diode converting AC voltage to DC voltage is shown on the animation below.

The setup of the above figure is a Full-Wave Bridge rectifier using 4 x 1N4001. Full-wave rectification is only achieved when four diodes are combined and linked to each other like on the figure above. A single package diode bridge is available in the market.


Signal Switching diodes are generally used for signal detection (i.e. AM signal detection, FM signal detection). In some circuits these diodes are also used as fuses for small amount of currents.

An example of an AM detector diode is the 1N60. The 1N60 is a Germanium Signal Diode housed in a DO-41 glass. Another example of an AM detector is a CDG00 AM detector diode. The availability of these diodes are very rare this days. If you ever find an electronics supply that sells it, it would be a good idea to buy the most you can for your future projects.

The 1N4148 Signal diode is also similar to an also famous 1N914 Signal diode. The availability of these diodes could differe from country to country. There is no big deal when you misuse a 1N4148 from a 1N914, they both perform the same functions.

From the photograph on the right. 1N4148 Switching Signal Diode (Left)
MMSD4148T1 Switching Signal Diode (Right)

The MMSD4148 is a surface mount version of the popular 1N4148, I got this diode from ON Semiconductors that was before their free sample program was free of shipping charges.



This type of diode is ideally suited for low voltage, high frequency rectification, or as a free wheeling and polarity protection diode.

This diode employs the Schottky Barrier principle with barrier metal that produces optimal forward voltage drop-reverse current tradeoff.

These diodes looks similar to the standard rectifier diode, so CARE SHOULD BE TAKEN when you are inserting these diodes, ALWAYS READ the part number written on the face of the component to be sure that the part you are inserting is the real one.

The Schottky Diode is best used for high frequency rectification commonly used in Switched Mode Power Supplies (SMPS).

1N5822 Schottky diode

back to top LED (Light Emitting Diode)
LED Schematic representation

LEDs are so popular in electronics. They are used in many applications from toys, flashlights, computer peripherals, digital cameras, cellphones, etc.

My first electronic circuit was to light an LED and sadly It was destroyed because of high voltage. That was before, but now I know how these little things work and I'm enjoying every thing about it.

The figure on the left(top) is the schematic diagram representation on an LED.

LEDs comes in various colors the photo on the left(bottom) shows three different colors of leds. The clear LED can be thought of as a white LED, infact it's just casing. The clear LED can have other variations of color like bright red, blue, bright green.

The clear/transparent LEDs gives a much brighter intensity of light that it emits.

The color that an LED emits depends on the gas used inside it.