ElectoWorld

  Diode is a non-linear, polarized electronic component. The direction of connection of the diode therefore has an importance on the operation of the electronic circuit.  It is a dipole that only allows electric current to flow in one direction. This dipole is called a rectifier diode when it is used to make rectifiers that transform alternating current into unidirectional current. Diode Symbol In the category of diodes, there are also regulation diodes, called zener diodes, which behave as a voltage source. This property will make it possible to develop around this simple component a whole series of assemblies delivering one or more direct voltages. Operation The diode is a switching component which has 2 operating modes: • Diode in the state: On. • Diode in the state: Blocked. The diode can switch from on to off state. Current-voltage characteristic of the diode: Above a certain positive voltage Vd threshold Vo, the forward current increases very rapidly with Vd...

It should be noted that the operational amplifier is an active component and that it has a low output impedance. Namely that he will be able to behave like a source of tension.  This is useful when you apply a voltage with low load carrying capacity as input. We will speak of a "buffer" stage. it is designed to allow impedance matching between two successive stages of a circuit. Of course, this does not go without modification of the input signal: it is therefore necessary to be careful with the offset introduced by the AOP, the distortion that it will insert on the input signal, its band gain product and thus its be able to correctly pass high frequency signals,Note that the input and output are not reversed. Linear applications 1) Voltage follower amplifier Follower op amp b) formula Vout = Vin c) Remarks The resistance at the input of the assembly is infinite. The voltage follower makes it possible to take a voltage without disturbing it, because it has...

A variable resistor is a resistor whose value is variable.many factors can induce a variation of R according to its constitution. The most common are the following factors: Mechanical: Most often a variation in the length of the resistant body. These are strain gauges, Potentiometers or Rheostats. Thermal: The temperature to which the resistance is subjected (thermistor). We can find the Positive Temperature Coefficient resistance (the resistance increases when the Temperature increases) and the Negative Temperature Coefficient (the resistance decreases for an increase in T). Radiation: The radiation to which the resistance is subjected. (Many models exist, each one is sensitive to a specific radiation range). Chemical: A substance (gas, liquid, solid) brought into contact with the resistance. Electrical: the varistor is a resistor whose value drops from a threshold voltage. NTC Thermistors  Thermistors or resistors with negative temperature coefficient or N...

  Definition An instrumentation amplifier is an electronic device for processing weak electrical signals. The typical application is the processing of signals from measurement sensors. Its operation is based on the principle of differential amplification. The instrumentation amplifier is generally made from one or more operational amplifiers, in such a way that it improves their intrinsic characteristics: offset, drift, amplification noise, open loop gain,  common mode  rejection ratio (CMRR), input impedance. fig 1 :instrumentation amplifier The first stage: we will use the fact that the inputs v + and v- of the amplifiers are equal, and that the input impedances are infinite. the current flowing in Rg and in the two resistors R is the same, so We can write: V1 − V2 = Rg× i Vod = (2R+Rg) x i Vod = (V1-V2) x ((2R+Rg) /Rg) The common mode voltage at the input of the assembly is: (Vcm)input = (V1+V2) / 2 the common output mode is equal to: (Vcm)output= (Vo...

The thermistor is an element that detects temperature. It is made of a semiconductor material that captures all temperature changes. They have negative temperature coefficients. In this case, the resistance of the thermistor decreases when the temperature increases, this one is then also called NTC thermistor. When the Joule effect (heating due to the passage of current) is negligible, we can express a relation between the resistance of the NTC and its temperature by the following relation: The temperatures are  in degrees Kelvin, B and T0 are constants of the component.. NTCs are made from oxides of transition metals (manganese, cobalt, copper and nickel). These oxides are semiconductors. Characteristics: NTCs can be used in a wide temperature range, from -200 ° C to + 1000 ° C, and they are available in different versions: glass beads, discs, bars, pellets, washers, chips etc.  The nominal resistances range from a few ohms to a hundred kohms. The response time depends ...

A photo-transistor is an electronic component capable of reacting to light by letting current flow. Like transistors, the photo-transistor is designed according to a base, emitter, a collector. But the base is sensitive to light and therefore controls the flow of current through the collector. The photo-transistor is much more sensitive than a photo-diode. A classic photo-transistor-based assembly is the Darlington: a photo-transistor controls a classic transistor, which is very efficient for light barriers or obstacle detection. Phototransistor  Symbol The phototransistor is manufactured most of the time in silicone, but also in other materials (ceramic, and others). The phototransistors are enclosed (generally) in a small opaque or transparent shell, in order to strengthen the light that passes through it and allows light to reach sensitive areas of the phototransistors. How a phototransistor works ? A phototransistor is a transistor whose base B is controlled by the lighti...

a capacitor is a component made up of 2 parallel conductors, called plates separated over the entire extent of their surface by a thin insulator, expressed by its dielectric strength ε r (epsilon) or relative permittivity. The capacitor is an electronic component which has the particularity of being able to store energy when it is subjected to a voltage. This component is essential in the field of electricity, it is almost as common as resistance. Capacitor Symbol Charg e and energy stored in a capacitor The charge that can be stored in a capacitor of capacitance C in farad is given by the formula: Q =  C x  U The constants of this equation are : C: capacitor capacity in Farads (F) Q: capacitor charge in Coulombs (C) U: voltage across the capacitor in Volts (V) Definition of farad: capacitance of a capacitor containing 1 coulomb under 1 volt. The energy stored in joules can be calculated with:  Electrical model of real capacitors the manufacturing method and...

A photocoupler, or optocoupler is a device that allows two circuits to be connected and electrically isolated, we will have a control circuit with low currents which will drive a power circuit who will have current more important. how does an optocoupler work ? Provide galvanic isolation between two different circuits, while allowing the transmission of logical or analog information. The transfer of information between the two circuits takes place in a closed environment and is achieved by a luminous flux of wavelength l. The light is transmitted inside the case through a transparent plastic film. The LED lights up, the phototransistor receives light: the phototransistor is saturated  (switch closed). The phototransistor is not receiving light (the LED is off or an object interrupts the  light beam), the phototransistor is blocked (switch open) Why use an optocoupler? The role of an opto-coupler is either to provide galvanic isolation (no electrical connection) b...

Electromechanical relay An electromechanical relay is a switch controlled by an electromagnet. It is used to isolate the control circuit (which operates the electromagnet) and the power circuit (which is controlled by the switch) from each other. There is then no conductive connection which would allow the current flowing in the power circuit to damage the control circuit. R elay coil voltage For each relay, there is a coil voltage. It can be continuous (5V, 12V, etc.) or alternative (110V, 230V). This is the voltage that must be applied to the coil to switch the relay. The current consumed depends on the type of relay and is inversely proportional to the coil voltage. In a range of relays (5V, 12V, 24V, etc.), the power of the coil is constant For example: 12V 40mA, 24V 20mA, 48V 10mA, etc ... To determine the current consumed by the coil, simply measure the resistance with the ohmmeter and deduct the current. This is useful for dimensioning the power supply to the control (the ci...

Metal-oxide semiconductor field-effect transistor (mosfet) is the second type of field-effect transistor. The mosfet gate is a channel isolated by a layer of silicon dioxide (Si02). The drain and the source are made from substrate materials. they are connected to the gate by a narrow channel. Transistor has type of metals. The first is called the mosfet at depletion and the second is called the   enhancement mosfet (E). The MOSFET transistor is different from the JFET in that the gate is isolated from the channel. Like diodes, these elements are most often made of silicon. They are used to make amplifiers. The enhancement MOSFET In the absence of a control signal at the Gate (Vgs = 0V), the Mosfet is blocked regardless of the type of channel (N or P).Conduction only begins to manifest from a threshold:+ Vth for Drain an N-channel MOS and –Vth for a P-channel MOS. N-channel   enhancement mosfet is a positive voltage applied to the input. The positive charge sticks...

The integrated circuit NE 555 enables the astable and monostable functions of long duration which allow the realization of time delays ranging from a few microseconds to a few hours.  Its performance and ease of use have opened up areas long reserved for electromechanics. The NE 555, which is in the form of an integrated circuit with 8 terminals, represents today one of the most used solutions for the generation of rectangular signals. ic 555 pin diagram As shown in the pinout in Fig1,  the 8 terminals of circuit NE 555 are: 1 ground (0 V supply) 2 trigger input 3 the main outlet 4 Reset input (Reset to Zero) 5 control output 6 threshold input 7 unloading exit 8 power supply (voltage VCC) the internal principle of 555: the Circuit NE 555 therefore has 3 inputs, 3  outputs, and 2 power supply terminals. We will call V2 the voltage present on terminal 2 (trigger), V6 the voltage on  terminal 6 (threshold), V5 the voltage on terminal 5 (control),...