Electronics is the study and use of electrical components and circuits to achieve a design goal.
The main parts, or electronic components, used in electronics are resistors, capacitors, coils of wire called inductors, integrated circuits, connection wires, and circuit boards. Older electronics used glass or metal vacuum tubes to control the flow of electrons. By the late 1960's and early 1970's the transistor, a semiconductor, began replacing vacuum tubes as control parts. At about the same time, integrated circuits (miniature semiconductor circuits containing large numbers of very small transistors put on on very thin slices of silicon) came into general use. Integrated circuits not only made it possible to significantly reduce the number of components needed to make electronic products, but also made them much more reliable and at a lower cost.
People interested in physics often study how and why these electronic components work. By their studies they are able to discover, invent, or improve electronic components. Other people design and construct electronic circuits, using these components, to solve practical problems. These people are a part of electrical, electronics and computer engineering field.
Most electronic systems fall into one of these two categories:
Processing and distribution of information. These are communications systems. Conversion and distribution of energy. These are control systems. One way of looking at an electronic system is to separate it into three parts:
Inputs - Electrical or mechanical sensors (or transducers), which take signals (in the form of temperature, pressure, etc.) from the physical world and convert them into current and voltage signals. Signal processing circuits - These consist of electronic components connected together to manipulate, interpret and transform the information contained in the signals. Outputs - Actuators or other devices (also transducers) that transform current and voltage signals back into useful physical form. Take as an example a television set. A television set's input is a broadcast signal received from an antenna, or a wire cable provided by a cable television vendor. Signal processing circuits inside the television set use the brightness, colour, and sound information contained in the received signal to control the television set's output devices. The display output device may be a cathode ray tube (CRT) or a plasma or liquid crystal display screen. The audio output device might be a magnetically driven audio speaker. The display output devices convert the signal processing circuits' brightness and colour information into the visible image displayed on a screen. The audio output device converts the processed sound information into sounds that can be heard by listeners.
Analysis of a circuit/network involves knowing the input and the signal processing circuit, and finding out the output. Knowing the input and output and finding out or designing the signal processing part is called as synthesis