Internet Guide to Electronics 

  When a beginner to electronics first looks at a circuit board full of components he/she is often overwhelmed by the diversity of do-dads. In these next few  sections we will help you to identify some of the simple components and their schematical symbol. Then you should be able to call them resistors and transistors instead of "Whatchamacallits". In later sections we will go into the workings of each component.  Just try to familiarize yourself with the basics for now. 

Electronic component are classed into either being Passive devices or Active devices. 

Active Devices are components that are capable of controlling voltages or currents and can create a switching action in the circuit. In other words, "Devices with smarts!" Examples are Diodes, Transistors and Integrated circuits.

NOTE: Most Active components are semiconductors. More on this in later sections.

A Passive Device is one that contributes no power gain (amplification) to a circuit or system. It has not control action and does not require any input other than a signal to perform its function. In other words, "A components with no brains!" Examples are Resistors, Capacitors and Inductors  

Diodes are basically a one-way valve for electrical current. They let it flow in one direction (from positive to negative) and not in the other direction.  Most diodes are similar in appearance to a resistor and will have a painted line on one end showing the direction or flow (white side is negative). If the negative side is on the negative end of the circuit, current will flow. If the negative is on the positive side of the circuit no current will flow. More on diodes in later sections.

LEDsLEDs: Light Emitting Diodes:
LEDs are simply diodes that emit light of one form or another. They are used as indicator devices. Example: LED lit equals machine on. They come in several sizes and colors. Some even emit Infrared Light which cannot be seen by the human eye.

The transistor is possibly the most important invention of this decade.  I performs two basic functions. 1) It acts as a switch turning current on and off. 2) It acts as a amplifier. This makes an output signal that is a magnified version of the input signal. More on transistors in later sections.
   Transistors come in several sizes depending on their application. It can be a big power transistor such as is used in power amplifiers in your stereo, down to a surface mount (SMT) and even down to .5 microns wide, such as in a microprocessor or Integrated Circuit.

Integrated CircuitsICs -Integrated Circuits:
Integrated Circuits, or ICs, are complex circuits inside one simple package. Silicon and metals are used to simulate resistors, capacitors, transistors, etc. It is a space saving miracle. These components come in a wide variety of packages and sizes. You can tell them by their "monolithic shape" that has a ton of "pins" coming out of them. Their applications are as varied as their packages. It can be a simple timer, to a complex logic circuit, or even a microcontroller (microprocessor with a few added functions) with erasable memory built inside.

MICROPROCESSORSMicroprocessors (MPUs):
Microprocessors and other large scale ICs are very complex ICs. At their core is the transistor which provides the logic for computers, cars, TVs and just about everything else electronic. Packages are becoming smaller and smaller as companies are learning new tricks to make the transistors ever tinier.