Earlier this month while driving to astronomy outreach program on a winter night, a friend of mine was telling me about his audio cassettes collection and portable cassette player. Discussion went on to electronic gadgets and at the end I was stumped by his question – “what makes a small device to store thousands of songs? What is so special about silicon in electronics?” I didn’t speak a word for next few minutes, and then I started talking. I told him about semiconductors, transistors, ICs, programming, storage… NOT in this order. For next fifteen-twenty minutes I spoke whatever I learned to get Diploma and Degree in electronics engineering. Sadly at that time what I told him was not helping to clear concepts and he literally went on back seat to sleep! :P Now let’s see what Electronics is !?!
Electronics axiomatically is about electrons and when studying it one has got to learn this
- Flow of electrons is “Current”. This current flows from higher potential to lower potential.
- This difference between potentials is called as “voltage”.
- Silicon is semiconductor which is why it is widely used in Electronics.
Almost all electronic gadgets / instruments / control systems are generally box shaped (or whatever aesthetically looks good). It has knobs, buttons, displays termed as user interface (UI). It enables user to operate the system. If it is computer system, it process information and stores it. If it is control system, it controls to operation of machines connected to it. If it is communication system, it transmits/receives the electro-magnetic signals. So it can be said that today’s electronics isn’t stand alone system. It is merged with computers, mechanical and communication systems. Although technically electronics systems can be categorized as Analog and Digital, it is hard to differentiate it by looking from outside. Today’s systems are intelligent because of digital computing systems. It senses its own performance, environment in which it’s working and tries to perform at optimum level all the time.
Electronic System is pretty simple to define in one line. It takes input, processes it and delivers output. Electronic system needs power supply to work. Power supply injects electrons in the circuit. Circuit is a center of every electronics system. Circuit physically is a board (PCB) with lots of electronic components, devices mounted on it and connected with others by conducting tracks on a board in a designed manner. Circuit itself is designed to work or designed to make sure that system works exactly as it is intended. When power is applied, each component in electronics exhibit unique specific characteristics. Basic components of electronics are Resistor, Inductor and Capacitor. It also includes semiconductor components and hi-tech semiconductor devices. Combination of various components and devices serves the purpose.
IC to Atom, Atom to IC.
When we see PCB, first attractive thing we notice on it is black chip which looks like tiny creature having lots of legs. It is called integrated circuit chip (IC). We should thank Nobel laureate Jack Kilby for the invention of Integrated Circuits at Texas Instruments. The rapid development of Computer technology is because of IC. Since 1960’s capability of fabricating more complex circuit on compact IC is increasing. IC is composed of thin (nanometre) silicon wafer on which “many” transistors are etched (analogous to carve) and are interconnected in a specific manner. For physical connection metal connecting pins are taken out. Whole thing is fabricated in ceramic (Black structure) with standard packaging shapes. Analog applications ICs are signal amplifier, frequency filters etc. Digital application ICs are Digital logic gates, micro-controller processors, memory storage. There are lots of steps involved from designing to manufacturing of IC – Shown in short in next image.
- IC DS1307 is real time clock. It counts each second, minute, hour, day and date. This data can be fetched by micro-processors at any instant.
- IC LM324 contains four operational amplifiers which can be used as comparator. Compares two signals and tells which is high or which is low.
- IC 555 is popularly used as timer.
- According to Moore’s Law the number of transistors on integrated circuits doubles approximately every two years. Now period is often defined to 18 months.
- Intel’s Core i7 processor was introduced in 2008. Its size is 263 mm^2 and contains 731,000,000 transistors.
Before the invention of IC, there was important breakthrough in 1947 – Invention of transistor at Bell telephone labs. There was need of less bulky components than Vacuum Tubes which were slow, big with several other operational drawbacks.
Silicon is semiconductor which has 4 electrons in its outer-most shell. One atom of silicon bonds with other four electrons. So no electron is free to carry the current. When impurities like Phosphorus and Boron are added in pure Silicon it forms N type (One electron free to go in conduction band) and P type (One Hole free) silicon respectively. When P type and N type material are connected together, a junction is formed. This junction restricts the charged carrier to “move” from one type to another. Consider this as “OFF” state. But when appropriate external power supply is given, junction can be made open and current starts flowing. Consider this as “ON” state. Thus semiconductor silicon with additional impurities can make a components which can be operated as conductor / non-conductor as per requirement. This characteristic is basic building block of electronics.
Diodes, Transistors and Thyristor family components (Widely used in Power electronics) are fabricated using various combinations P type and N type materials. We can control flow of electrons through components, electron density in a current, Voltage levels and thereby power level of a signal.
A transistor in a circuit can be used as Amplifier, Switch and regulator. Transistor as a switch is vital in digital electronics. Digital electronics works only on 2 states. – Logic 1 and Logic 0. Transistors can switch between ON/OFF state more than thousand times per seconds. High speed transistors have switching speed more than that. This corresponds to state of the transistor ON and OFF. Hold this thought in a mind.
Programming Micro-controller (High Techy Techy!)
Suppose I want to design a system. There is a key / Button named K1. The moment K1 is pressed, digital display should show message “Gotcha !” For this there is need of a device, which senses “key pressed” event and drives digital display to show message. So microcontroller (uC) IC chip is used.
A program i.e. code is written to continuously monitor a key connected to uC. As soon as key is pressed uC sends commands to digital display to be ready; Transfer a data i.e. message from uC to display; Latch data display’s memory and finally show it.
For every operation above, instructions (Pre-defined instructions provided by manufacturer) are written in specific programming language on a computer. Each instruction programmer writes, software converts it into HEX code (Hexa-Decimal number system – 0 to 9 and A to F) – machine language. Hence here is conversion of programming language into HEX code. Final code is needed to download into the uC. Downloader converts Hex code into Binary code (0 and 1). Hence whole program including message “Gotcha !” is now in the Binary code. All 0s and 1s.
On other side, Printed circuit board is designed to make connection between a key as input to uC and output from uC through data cable to digital display. Power supply is connected wherever necessary.
As told earlier
- Each instruction has unique code.
- ICs are made up of transistors.
- Transistors can switch between ON/OFF state.
uC reads “Binary code” of a instruction of program download into its ROM, specific “set of transistors” becomes active and turns ON/OFF accordingly. This is called as execution of an instruction. This happens every time, for every instruction.
Digital Display also has its own processor. It differentiates between commands and data coming in and shows message accordingly.
Memory: ROM, PROM, EROM, EEPROM, FLASH. These are types of memory chips. Earlier memories were only read only memory. Then came programmable ROM. User could write data into it but could not erase it. After that new memory chips were manufactured. Exposing chips to UV light could erase its content. New Chips after that used to be erased by electricity. Now we use Flash memories in which data read/write can be done in fraction of a second. According to data, bit by bit transistor is turned ON or OFF. So very roughly one transistor along a capacitor holds i.e. stores one bit of data (This sentence isn’t totally correct).
Similarly, many components /devices / technologies are invented / improved which can be categorized in “n” number of sub-fields of electronics. Sensors, actuators, transmitter/receiver, antennas, semiconductor materials, micro-processors, VLSI technology, displays, batteries, Digital Signals processors, communication protocols, filters, amplifiers, transformers, electro-mechanical switches, lighting, etc etc etc…
The “flow of electronics” is now one of the reasons why we live cherished life.
Also check this classic XKCD – http://imgs.xkcd.com/comics/circuit_diagram.png