Electronic Circuits

Electronic circuit is composed of individual electronic components such as resistors, transistors, capacitors, inductors, and diodes connected by conductive wires or traces through which electric current can flow .The combination of components and wires allow various operations such as amplification of signals, computations and transfer of data from one place to another. Circuits can be constructed from discrete components connected by individual pieces of wire, but now the interconnections are created by photolithographic techniques on a laminated substrate (a printed circuit board) and solder components to these interconnections to create a finished circuit.

Bread boards, perfboards or strip boards are common for testing designs. They allow the designer to make quick changes to the circuit.

An electronic circuit can be categorized as follows:-

1.      Analog circuit. 

2.      Digital circuit. and

3.      Mixed-signal circuit.

1.      Analog Electronic Circuit:-

Analog electronic circuits are those in which current or voltage may vary continuously with the time to correspond with the information being represented. Analog circuitry is constructed from two building blocks namely series and parallel circuits. In the series circuit, the current which is passed through all the series components will be same. In the parallel circuit, all the components are connected to the same voltage, and the current divides various components according to their resistance. The basic components of analog circuits are wires, resistors, capacitors, inductors, diodes and transistors (Recently memristors have been added to the list of available components). Analog circuits are very commonly represented in schematic diagrams, in which wires are shown as lines, and each component has unique symbol. When the size is comparable to wavelength of relevant signal frequency, a more sophisticated approach must be used. Wires are treated as transmission lines, with constant characteristic impedance, and the impedances at the beginning and end determine the transmitted and reflected waves on the line.

                                                                           

2. Digital Electronic Circuit:-

In digital electronic circuits, electric signals take on discrete values, to represent the information that is being processed. In the vast majority of cases binary coding is used. Digital circuits make extensive use of Transistors, interconnected to logic gates that provide the functions of Boolean logic. Transistors interconnected so as to provide positive feedback are used as latches and Flip-flops. Digital circuits therefore can provide both logic and memory, enabling them to perform arbitrary computational functions. (Memory based on Flip-flops is known as SRAM (Static Random Access Memory).

Memory based on storage of charge in a capacitor, DRAM (Dynamic Random Access Memory) is also widely used).

Digital circuits are very easy to design when compared to analog circuits for the same level of complexity, because each logic gate regenerates the binary signal, so the designer need not account for distortion, gain control, offset voltages, and other concerns faced in an analog design. As a consequence, extremely complex digital circuits, with billions of logic elements integrated on a single silicon chip, can be fabricated at low cost. Such digital integrated circuits are ubiquitous such as calculators, mobiles, computers...

Digital circuitry is used to create general purpose computing chips, such as microprocessors, & custom designed logic circuits, known as Application Specific Integrated circuits (APSIC’s). Field Programmable Gate Arrays (FPGA’s), chips with logic circuitry, whose configuration can be modified after fabrication, are also widely used in prototyping & development.

                               

3.      Mixed Signal Circuits:

Mixed signal or hybrid circuits contain both analog & digital circuits. Examples include comparators timers, PLLs, ADCs (analog to digital converters), & DACs (digital to analog converters).

Most modern Radio & Communication circuitry uses mixed signal circuits. For example in a receiver analog circuitry is used to amplify the frequency so that they reach the suitable state to be converted into digital values, after which further signal processing can be performed in digital domain.