Circuits and YOU!

We've covered the 3 fundamental components the basis for electrical systems. Lets do a quick review over some terms

AC: Alternating current, circuit that deal with a cyclic harmonic change in potential over time. Us outlets are 110 VRMS 60HZ which means the average voltage put out is 110 volts and it oscillates as a 60HZ sine wave.

DC: Direct current, current is steady and a fixed potential is across two points. We use DC for most circuits.

Voltage: Potential difference across two points, Voltage is the work a circuit is capable of doing and is the product of an electrostatic attraction between two points.

Current: Is the charge that actually "flows" in a circuit. Voltage is the work capable current is what does that work.

The Three Fundamental components:

The Resistor: The resistor allows you to control current in a circuit, it is probably the most essential component. (V=IR)

Capacitor: Two plates separated by some sort of dielectric, Holds a charge and useful in storing energy and filtering signals.

Inductor: Coil of wire that holds energy in a magnetic field. Any current flowing through a wire produces a magnetic field around it.

The Fourth fundamental component?:

Resistors, Capacitors and Inductors are all useful things but it wasn't until semiconductors that we truly were able to create high speed circuits of today.

I've already done a writeup on semiconductors here:

http://mcuplace.com/mcu/blog4.php/2008/08/20/semiconduct-this

What is circuitry?

Circuitry is the process of taking these components and making circuits that do useful things. We can make sensors that record data, Counters, Timers, Computers, Calculators, Robots. We can make pretty much anything you want to with these components.

What we will be covering in this blog is a hodgepodge of information from digital circuits, to circuit analysis to schematic design and introduction to software suites.

Basic Symbols:

Part of reading a schematic is understanding what the symbols mean and how to interpret them.

Voltage Source / EMF

A battery or DC voltage source is denoted by parallel lines of varying size. The longer line denotes + and smaller line denotes -

Passive Components:

The symbol for a resistor is a zig-zag line.

Potentiometers or variable resistors are a resistor symbol with an arrow through it

The symbol for a capacitor is two separated parallel lines

Electrolytic capacitors may have a curved line or a + sign to denote polarity

The symbol for an inductor is a half coil

Semiconductors

The symbol for a diode is a triangle with a line at the tip, the triangle *points* where the current flows and the line is usually on the negative part of the diode.

The symbol for an LED is a diode symbol with arrows coming out from the triangle denoting it produces light.

Transistors

NPN Bi-polar Junction Transistors are denoted by the following symbol

PNP transistors are denoted by

NPN can be remember because the arrow is Not Pointing iN, and PNP is the complement of NPN

MOSFET transistors share a different symbol than BJT transistors.

NMOS transistors are denoted by:

PMOS are denoted by a NMOS symbol with a complement dot in the front.

MOSFET transistors also have different symbols but all use the same basic shape.

There are many other symbols out there for electric components, however these are the most common. As we demonstrate more circuits we will go over the symbols as we get to them.

We will be going over some basic circuits so we can get the hang of designing circuits and doing analysis.