Electronics | FatmahEl-Ghandour

Introduction to Electronics

Lets start introducing electronics by defining the most used components in any circuit. Before getting along into the details, I would just like to point out how fun and amusing it is. You can make more when you know more, So never hesitate to learn more about components.

You can explore more about soldering and/or PCB designing from visiting these links.

Wire: A conducting connection between two nodes/component. We mostly use jumpers Male-Female or Male - Male.

Button: Its more of a switch but needs human action, you press it the circuit allows current circulation and vice versa.

Switch: In electronics, an electronic switch is an electronic component or device that can switch an electrical circuit, interrupting the current or diverting it from one conductor to another. See symbol>>>

Resistor: They are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

Capacitor C = Q/V , I = C * dv/dt: A device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator.

Inductor V = L * di/dt: A component that stores energy in a magnetic field when electric current flows through it.

Diode: a semiconductor device with two terminals, typically allowing the flow of current in one direction only- Anode to Cathode only.

Schottky: The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action.
Zener: is a particular type of diode that, unlike a normal one, allows current to flow not only from its anode to its cathode, but also in the reverse direction, when the Zener voltage is reached.

LED: A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated.

Transistor: a semiconductor device with three connections, capable of amplification in addition to rectification. (NPN)

Bipolar transistor: amplifies current, but it can be connected in circuits designed to amplify voltage or power.(PNP)
Mosfet: The metal-oxide-semiconductor field-effect transistor is a type of field-effect transistor, most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, whose voltage determines the conductivity of the device.

Power Supply : The primary function of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load.

Battery: It is a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit. All batteries are made up of three basic components: an anode (the ‘-’ side), a cathode (the ‘+’ side), and some kind of electrolyte (a substance that chemically reacts with the anode and cathode).

Op-amp: An operational amplifier is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.

Micro-controller and Microprocessor: A microprocessor is an Integrated Circuit (IC) which has only the Central Processing Unit (CPU) inside it. They lack Random Access Memory (RAM), Read Only Memory (ROM), and other peripherals on the chip. Unlike microprocessors, micro-controllers possess a CPU along with RAM, ROM, and other peripherals on the same chip.

Sensors: Devices that detect and respond to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena.
Actuators: A type of motor that is responsible for moving or controlling a mechanism or system. It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion.

Multi-meter: It is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance.

Oscilloscope: It is a laboratory instrument commonly used to display and analyze the waveform of electronic signals. In effect, the device draws a graph of the instantaneous signal voltage as a function of time.

Why batteries of different sizes have the same voltage?

A cell is a single electrochemical device, consisting of two plates and an electrolyte - the voltage of the cell is determined by the materials used. Every set of materials has a electrochemical voltage associated with it. The voltage is determined by the type of material, not the size or quantity.
A battery is made up of series connected cells and will have a voltage that is an integral multiple of the cell voltage.
Thus single cell batteries such as AA, AAA, C, and D all have the same voltage. The amount of material inside affects the total charge available. So bigger lasts longer.
Multi-cell batteries such as the 9V rectangular battery have 6 small cells inside, amounting to 9V. Its capacity is not very high due to the tiny cells crammed in there but the voltage is compensating higher which gives some advantage for things that require higher voltage.
To sum thing up the difference in the capacity is the difference between the two batteries of the same voltage but one life longer than the other.

What is Successive Approximation ADC??

Successive approximation ADC (Analog to Digital Converter) is the advanced version of Digital ramp type ADC which is designed to reduce the conversion and to increase speed of operation. The major draw of digital ramp ADC is the counter used to produce the digital output will be reset after every sampling interval. The normal counter starts counting from 0 and increments by one LSB in each count, this result in 2N clock pulses to reach its maximum value.

In successive approximation ADC the normal counter is replaced with successive approximation register as shown in below figure.

The successive approximation register counts by changing the bits from MSB to LSB according to input. The detailed operation is shown below.

Operation of 3 bit Successive Approximation ADC

The output of SAR is converted to analog out by the DAC and this analog output is compared with the input analog sampled value in the Opamp comparator. This Opamp provides a high or low clock pulse based on the difference through the logic circuit. In very first case the 3 bit SAR enables its MSB bit as high i.e. ‘1’ and the result will be “100”. This digita output is converted to analog value and compared with input sampled voltage (Vin). If the deference is positive i.e. if the sampled input is high then the SAR enables the next bit from MSB and result will be “110”. Now if the output is negative i.e. if the input sampled voltage is less than the SAR resets the last set bit and sets the next bit and resultant output in this case will be “101” which will definitely approximately equal to the input analog value. The counting sequence is explained by the following counter flow chat as shown in below.

Successive Approximation ADC Counter Flow chart

Conversion time of Successive Approximation ADC

By observing above 3 bit example it is illustrated for a 3 bit ADC the conversion time will be 3 clock pulses. Then;

N bit Successive Approximation ADC conversion time = 3T (T- clock pulse).

So to avoid aliasing effect the next sample of input signal should be taken after 3 clock pulses.

Important note on Successive Approximation ADC

In Counter type or digital ramp type ADC the time taken for conversion depends on the magnitude of the input, but in SAR the conversion time is independent of the magnitude of the input sampled value.

Advantages of Successive Approximation ADC

Speed is high compared to counter type ADC.
Good ratio of speed to power.
Compact design compared to Flash Type and it is inexpensive.

Disadvantages of Successive Approximation ADC

Cost is high because of SAR
Complexity in design.

Applications

The SAR ADC will used widely data acquisition techniques at the sampling rates higher than 10KHz.