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1. Sample and hold circuit Definition and Introduction Sample and hold circuit is an electronic circuit which makes the samples of input voltage signals and holds these samples signal for some very small time duration. Sample and hold circuit is basically is an analog to digital converter circuit. Input voltage signals to be sampled and hold for some duration (in microseconds) using the capacitor and give the output in the form of digital pulse. Because this works by the holds the sampled analog input signal this is called the sample and hold circuit. Holding of the signal is done using a capacitor called holding capacitor, capacitor has the ability to store the voltage by charging until it will discharge. This charging and storing property of the capacitor is used here for the holding of the signal. Sample Some Parts consider or Take the values of a given continuous input signal at each different time is called sample. Hold catch the sampled signals and take hold for a time t is called hold. Sampling time The time during which generates the samples of input signals called sampling time. This is usually 1us to 14 u sec. Holding time The time during which the circuit holds the sampled value is called the holding time. Holding time to be set according to the required for application. Basic sample and holding circuit A basic sample and hold circuit consists a switch and a capacitor. A combination of a control switch and a capacitor is called a simple sample and hold circuit. Input voltage applied at the point Vin and then a switch connected after that a capacitor connected between the switch and output. One side of the capacitor is connected with the ground. A JFET or a MOSFET is used as a Control switch. Working When the switch is closed the connected capacitor charged and when the switch is opened the capacitor will not get discharged because there is no path for discharging and then the capacitor takes to hold the signal. Sample hold circuit using op-amp In this circuit two voltage follower circuit, a capacitor and A MOSFET connected. Input voltage given at The control voltage is given on the gate terminal of MOSFET, here MOSFET is used as a switch. The reason of using the Voltage follower circuit is this circuit gives output same as the input signal and there is a very high input impedance so no load is considered at the input and the capacitator will also not get discharged because of very high impedance at the input of the op-amp. The MOSFET is used here as the control switch for applying the voltage pulse. The Gate terminal of MOSFET is connected with a controlled pulsed signal generator. Astable multivibrator can be used to produce frequency. This astable frequency switch ON-OFF Very fast the MOSFET. By the ON-OFF, ON-OFF of the MOSFET a pulsed form of the input voltage signal is applied to the NON-Inverting terminal of Op-amp. The capacitor will charge as a pulse signal gets for the 1st pulse to its max level and this level is HOLD for a definite time by the capacitor because this capacitor will not discharge. And now the next pulse falls and the capacitor will again charge as this pulse voltage level and this level hold and this process is continuously proceeding as per pulse signal and the amplitude level of the pulse signal. So, in this whole process, the output is sampled and also hold for a time duration, these are done by the main capacitor used in this circuit. We know that the sampled signals are the digital signals, So we can say that the sample and hold circuit converts analog or continuous-time signal into digital signals. Uses or applications of Sample and Hold circuit ADCs (Analog-to-Digital Conversion) DACs (Digital-to-Analog Conversion) In Analog Demultiplexing In Linear Systems In Data Distribution System In Digital Voltmeters In Signal Constructional Filters more articles on www.circuitspedia.com/
2. Tone generator circuit using 555 timer Bird sound generator, Ambulance Siren Generator These are some circuit diagrams of the sound generators. Sounds are like Bird sound, Ambulance siren, Beep Horn, and other different types. Use 9 to 12v Dc supply and components value should be the same as suggested in the diagram because any variation of components value can change the sound type. By some changes of values of some components as given below in the diagram, you can produce many different type of sounds. Use a medium-size speaker, These circuits can be useful for the making of Alarm, Doorbell or other warning indicators. For more circuit diagram go to circuitspedia.com Testing Video Also read Bird sound generator using arduino UNO
3. why ac current passes through capacitor but dc can’t how capacitor block dc current Explanation 1 We try to understand using a discharged battery in the circuit. When switch on, the battery is starting to charge and increasing the voltage level of the battery and there is a flow of current. When the battery gets fully charged and the voltage of a battery increase and is equal to supply voltage then there is no flow any current between them. Let us consider a simple circuit as given below. In this circuit, a capacitor is connected with a resistor in series. A 12v DC power supply is used. This circuit is open because the switch of this circuit is open. In the case of capacitor If I turn on the switch then what will happen? After the supply used in this by turning on the switch, the Capacitor will start to Charge and this capacitor will charge continuously till the voltage is equal to supply voltage. Here 12v used so capacitor is getting charged from 0v, 1v, 2v,3v,4v……….upto 12v. And when capacitor charged with 12v then it will stop to charge. If supply is used of 9v then the capacitor will stop to charge after 9v. Now, we take a look at the following diagrams. A resistor of 2 ohm is in the diagram and one side of the resistor is voltage is 12v and the other side is 0v. So here is the potential difference between two points is 12-0=12v. Means voltage across the resistor is 12v. So the current conduction is I=V/R=12/2=6A. If other side voltage increases and becomes 6V then the potential difference is 12v – 6v=6v means voltage across the resistor is 6v. The current conduction is I=V/R=6/2=3A. So we see here if the voltage at the two-point in the circuit has much differed then the potential difference between them is high means the voltage level is high and there is high current flow. But if the voltage at two points in a circuit is Similar then the potential difference between them is 0, so the voltage is 0 between those two points. In this case, the current flow is 0/2=0A, which means no current flows. The same phenomenon occurs with the Capacitor. At starting when the Capacitor starts to Charge from 0v, A current flows through the capacitor in the circuit. But after some time when the capacitor gets fully charged and the voltage level of capacitor increase maximum or equal to supply voltage, then there are 0 potential differences and then no current flows across a capacitor. In the diagram, we see that the voltage level is equal to both sides of the resistor after a full charge of the capacitor, so there are no current flows across the Capacitor because of the potential difference across it become 0v. Actually capacitor doesn’t block DC current, the capacitor makes potential difference high to very low (about 0) and stops the current flow between them at a particular portion of a circuit by itself charge. But we feel like the Capacitor block DC current. Explanation 2 When switch on supply then Electrons start stored in the Capacitor and after some moments capacitor gets charged by Electrons and positive ions. After charging the Capacitor Electrons are repelled by charged Electrons and then the capacitor works like an open circuit. As formula Xc=1/2πFC In DC there is no frequency so F=0. So Xc=1/0=∞.means there is very high resistance across the capacitor. So in dc capacitor acts as an open switch after charge. In AC current there is frequency. So continuous changes in polarity between negative and positive and this reason capacitor don’t get charged. In ac, the capacitor acts as a short circuit. As formula Xc=1/2πFC In AC always some value of F. So always a reactance creates across the capacitor that allows flowing the current. Also read- Thevenin theorem How does a Relay work Flip-Flops, S-R and J-K Flip flop .
4. Comparator A comparator is a circuit that compares two input voltages or currents and gives output High or Low as per input signal. The Output is a digital form according to the input signal compared with the reference. Basically a comparator is used in electronics to compare the two Analog input signals given on both input terminals and we get the Digital output as High level or Low level. Comparator is used to sense the signal of a predefined rich level. If I set a level to sense then I can use a comparator to sense it when the input signal of this level cross more or below the level, suddenly the output is changed from Low to high and high to low. The comparators are used for so many electronics instrumentation for automation and drive different logic circuits. Difference between operational amplifier (op-amp) and comparator The symbol of the operational amplifier and comparator are looked the same. But Op-amp is designed to accept an analog input signal and also give the output Analog signal. But the Comparator accepts the analog input signals but gives the digital output. Comparators are faster than the operational amplifier. An op-amp will works as the comparator if using the transistor at the output. If the input is applied at the + pin, this is called non-inverting input If the input is applied at the – pin then this is called the inverting input Non-inverting mode If I connect the input voltage at the non-inverting input and set a reference voltage level at inverting input which is to be sensing. In this circuit, the voltage will compare with the reference. If the applied voltage is lower than the reference voltage then the output is LOW, and if the applied input voltage is greater than the reference voltage then the output will HIGH. Here High level means output is directly connected automatically with VCC and Low means Output is directly connected with Ground. For example, if we set the reference voltage at 6v, then when the input voltage increases to 6v then the output suddenly swings to HIGH and gives the voltage the same as VCC, Otherwise output gives the LOW or 0v voltage. Input voltage > Reference Voltage – Output HIGH Input voltage < Reference Voltage – Output LOW comparator circuit diagram Inverting Comparator In inverting mode the input voltage is connected with the Inverting terminal and reference voltage is st at the non-inverting terminal. In this connection, the voltage at the Inverting terminal will be sensed and compared with the voltage at the non-inverting terminal which is the reference voltage. The inverting mode comparator works reverse to the non-inverting comparator. Means If the voltage at Inverting terminal is greater than the Reference voltage then the output will LOW, But If the Input voltage is Lower than the Reference voltage than the Output Will HIGH. This comparator gives output Inverted of input. For example, Reference voltage adjusted at 6v, when the input voltage increases and goes to 6v then the output will suddenly swing to LOW or 0v. Otherwise, the output will HIGH and give the voltage the same as VCC. The LM358 is the very popular comparator ic used for general purposes. This ic has 2 opamp comparator. LM324 is also a very popular and most using comparator ic. It has quad op-amp comparator. Also Read Kirchoff's Law .
5. What is ohm’s law In the electrical field, Ohm’s law is a very important topic. This law is asked in almost all interviews and as basic fundamentals of electrical engineering for all who related to electrical engineering. This is a very important fundamental law that describes the Relation between Current, Voltage, and Resistance. There are three main quantities present in Electricity. An electrical circuit is made by these three Quantities Current (I), Voltage(V), and Resistance(R). There is no imagine the electrical circuit without anyone thing of them. And one other essential quantity is Load. Because the current is flowing only if there is any load connected with the circuit. Ohm’s law is given by a German mathematician George Simon Ohm, who formulated the law known after his name as Ohm’s law. Also read Thevenin Theorem Ohm’s law definition Ohm’ law states that if physical conditions (like- temperature, pressure, length, etc) are constant, then the voltage across the two terminals of conducting material is proportional to the current flowing through it. Ohm’s law formula Ohm’ law is expressed as V∝I In the given fig when we connect a battery across the conductor then an electric field E is created and electrons move to the reverse direction of the electrical field. If I consider a cross-sectional area in a conductor, Then the number of total charges passed across a cross-sectional area in one second, which is called Current in the conductor. Now if I increase the potential difference across the conductor, The electric field and magnitude are also increased and the forces of electrons are also increased and the magnitude of electrons is so increased. Now the all free electrons will move with more speed. That means the number of electrons that were crossed across the cross-sectional area will now be increased and a large number of electrons cross across the cross-sectional area of a conductor in one second. And we can say that the current is increased across that cross-sectional area. If the potential difference increased by doubled then the current will also be doubled and the potential difference is increased 3 times then the current will also be increased by 3 times. so we can say that the Voltage (potential diff) is directly proportional to the current (I). V∝I if we replace the proportionality sign by = we need to place a constant. here R is the constant of proportionality that can be placed here. So V= I.R, R is resistance. Means R is in the circuit provided R is kept constant. Resistance is a fixed quantity of a particular conductor. But if i change the conductor material then the Resistance will also be changed. Also when I changed the length or thickness of the conductor then Resistance will also be changed. V is the s.i unit of potential difference and Ω is the s.i unit of resistance. And I is the si unit of current. Ohm’s law is used to find the current, Voltage, and Resistance in a circuit. How we use the ohm’ law For example, in the given diagram a 9v battery is directly connected with an LED. This Yellow LED works with the 3v (only for example actual voltage for the yellow LED may different) and 20ma current, But in the diagram, the applied voltage is higher than required. If I give more power than this the LED will burn as shown in fig. So I need to drop the voltage and current as suitable with LED. Given LED voltage = 3v Supply voltage = 12v LED current = 20ma We need to drop the voltage for LED = 12-3 = 9v, It means we need to reduce 9v from 12v battery. So Take here V= 9v, Then V = I.R 20ma = 0.02A (1A=1000ma) 9= 0.02 . R, and R = 450Ω, It means we need to add a minimum of 450 Ω resistor with the LED for Proper working. This Relationship between current-voltage, Resistance is not apply to all non-metallic conductors. It does not apply to non-linear devices such as Zener diodes. Must Read What is comparator .
6. you connect the circuit before the starter, i mean the supply to the motor starter pass through this circuit Relay. You start the motor using start switch ,when tank will full, then automatic stop the motor.
8. Semiconductor P-N Junction Diode Working Principle Diode is the two terminal polarised electronic semiconductor device . One terminal is Anode(-) and other is Cathode(+). The cathode is marked with the silver colour or colour band. This is the simplest semiconductor device but this is very important and most useful in electronic circuits. Diode Function The main function of the semiconductor diode is the flow of electrons to totally in only one direction across it . It means Diode conducts current in only one direction. If change the polarity of diode then no any current passes through it. So we can say that diode is act as a switch which allow to conduction of current in only one direction. This is property of an Ideal Diode. An Ideal diode acts like short circuit with same polarity with supply, But in Reverse connection it acts like Open circuit means no any current flows in reverse polarity. The semiconductor Diode is formed by adding and apply a burning force or crystalization on together of P-type and n-Type materials (p-n junction). Joining of Both materials should of the same base - Ge or Si. The PN-junction is the basic root for semiconductor diodes . PN junction PN junction is made from a single piece of semiconductor of two different properties . One side is made to be P-type material and the other side is made with N-type. Both ends of the PN-junction have different properties. One end has an excess/majority of electrons and the other end has an excess/majority of holes. The p-type semiconductor is formed by adding trivalent impurities in pure or intrinsic semiconductor and n-type semiconductor is formed by adding pentavalent impurities in pure or intrinsic semiconductor. P-type materials have majority charge carriers of holes, and minority charge carriers of electrons. But in N-type materials have majority charge carriers of electrons and minority charge carriers of holes . Half part of a Si crystal is doped with trivalent impurity and half with pentavalent impurity, we get P-N junction diode. The border where p-type and n-region meets called the junction . The free electrons move from negative terminal (cathode) to the positive terminal (anode) . But the current flow direction is from positive terminal to the negative terminal. Forward bias- If p-terminal of diode is connected with positive supply and n-terminal is connected with negative supply then it is called forward bias. If the diode is forward biased, it allows the electric current flow. On the other hand, if the diode is reverse biased, it blocks the electric current flow. Reverse bias- When p- terminal of diode is connected with n-terminal of supply and n- terminal is connected with p, this connection is called Reverse bias connection. In this connection no Electrons flow and no current flows. • Depletion layer- Depletion layer created by the initial movement of majority carrier across the junction. Holes concentration on p- type and electron concentration on n-type are very high . Due to formation of p-n junction by diffusion electron moves from n-type to p-type and holes move from p-type to n-type. By the combination of electrons and holes at the junction creates ions, and there are presents only ions at the junction . Ions are non- movable. Therefore when holes passes to electrons through these ions, then +ve ions repels the holes and oppose it passing to electron, And created a resistance wall of very small width . This is called Depletion layer. Width of depletion increases in reverse bias connection. An electric field intensity is created with depletion layer. and the sign of this electric field is negative because the direction of electric fields is +ve to -ve. • Depletion layer consists +ve charge and –ve charge on either sides of junction. • Depletion layer opposes only the the majority carrier not minority carrier. • Depletion layer is also called Space charge region or transition region. • Depletion layer consists immobile charge particles. V-I Characteristics of Semiconductor P-N diode • Knee voltage- This is the minimum required voltage to start the conduction of current through diode. This is also known as cut-in voltage. This is the forward voltage at which the diode current starts increasing rapidly. The knee voltage of si diode is 0.7 voltage and 0.3v of Ge diode. • Breakdown voltage- This is the minimum amount of voltage of any insulator that makes it electrically conductor. In Reverse bias connection of pn diode. no any current flows through diode, but when we increase the reverse voltage level continuously Then diode get internally damage (breakdown) and start conduction at a fix level. Breakdown voltage is the minimum Amount of reverse bias voltage at which diode starts conduction in reverse bias connection. This breakdown characteristics of diode uses in Zener Diode which is always used in reverse bias and Limits the circuit voltage. • Doping- A material in pure form acts like insulator. So making it more conductive in nature we need to add some impurity to it. The process of adding impurities in pure (intrinsic material) is called doping to change their electrical properties.Generally trivalent and pentavalent elements are used to doping to semiconductor .When a semiconductor is doped with trivalent impurity(Boron,Aluminium) ,it becomes P-type semiconductor material. When dope any intrinsic material with Pentavalent impurity (phosphorus, arsenic,bismuth,antimony) then it becomes N-type semiconductor. • Reverse Saturation Current Both sides of p-n junction a very small amount of minority charge carrier present. P type minority charge carrier in n-type side and n-type minority charge carrier on p-type side.It also allows to flow a minority charge current. The current which is flowing by the minority carriers is called Reverse current. When a voltage applied on junction then further external reverse voltage flows due to minority charge carriers and this increases external voltage does not increases reverse current. At a voltage level where current goes on a fix maximum level and after Only voltage increases and curren does not increases . This is called reverse saturation current. Reverse saturation current remain constant with the increase of voltage, But when voltage will increase continuously then at a Level of voltage when junction will get breakdown and high reverse current will flow. Reverse saturation current depends on temperature. If temperature of junction increases , the minority charge carriers also increases. • The Width of Depletion Layer Practically The value of Depletion width vary from 0.1µm to 0.5µm Typical value of Depletion width is -0.5µm By increasing doping concentration Depletion layer width can Reduced electrons moves across the PN junction from the N-type to the P-type , they leave behind positively charged donor ions on the negative side. Holes from the acceptor impurity moves across the junction in the opposite direction into the region where there are large numbers of free electrons. As a result, the charge density of the P-type through the junction is filled with negatively charged acceptor ions , and the charge density of the N-type along with the junction becomes positive. This charge transfer of electrons and holes across the PN junction is known as diffusion . • Barrier potential/built in potential Simply Voltage form across the depletion layer is called the contact potential. The built-in potential in a semiconductor equals the potential across the depletion region in thermal equilibrium.This is also called built-in potential or barrier voltage/potential or potential hill or diffusion voltage. Contact potential always appear with in depletion layer It is noted as V0 or vbi. Contact potential of any diode can not measure by any instrument. V0 for Ge diode = 0.1v to 0.5v typically we use V0=0.2v V0 for Si diode = 0.6v to 0.9v typically V0= 0.7v Application of p-n junction diode • As Rectifier to convert AC to DC signal • Clipper circuit for clipping the signal (changing the wave shape) • To supply ( for protection from reverse supply) • Clamper circuit to restore the dc signal wave • As Voltage multiplier • In digital logic design • In Demodulation Circuits Other types of diode Photodiode, Zener Diode, Gunn Diode, Tunnel Diode. PIN Diode, Varactor Diode. Light Emitting Diode (LED), Schottky Diode, Laser Diode, Switching Diode. Also read 4017 Decade counter What is NOT Gate Inverter semiconductor diode.pdf
9. What is impedance (circuitspedia.com) Impedance (Z) is similar to Resistance (R) . Impedance and Resistance both oppose the current in circuit. Both are almost the same thing , But resistance related to DC Circuit. Resistance oppose the steady electric current in DC circuit. Resistance remains same (constant) at any different frequency range. Impedance is related with AC circuit. Impedance vary according to changing the frequency, this is not constant at different frequency range. Impedance also includes reactance (Inductive and capacitive property of the circuit). Reactance - Reactance is the Resistance produced to AC Currents by Inductors and Capacitors only. This is a measure of the type of opposition to AC electricity due to capacitance or inductance. The impedance is denoted by Z and unit of it is Ohm (Ω). If the level of ohm is higher then level impedance is also higher. Impedance = Resistance + Reactance (Either inductive or Capacitive or both) In DC circuit, Impedance is effective Resistance of the circuit. Z= R In AC circuits, it possesses both magnitude and phase, unlike resistance, which has only magnitude. In the case of capacitor, When the frequency increased then the resistance (Impedance ) of capacitor decreases. In Inductor this is just opposite, When we increase the frequency range then Impedance increase in inductor. Impedance Impedance is defined as combination of resistance and reactance. As we cannot assume any circuit with DC Current without Resistance , We cannot assume a circuit with AC current without Impedance. Resistive Power- Energy burns by resistive power to Heat goes through that system , In Reactive Power- the energy goes to Antennas, Speaker, transmission line, cable etc represents how much energy to be stored and propagates. Not burn to heat ie Impedance. Resistance If there is Only Resistor is connected with Load in any circuit then is called Resistor. • Reactance If any circuit there is Only inductor or capacitor connected with load. Then the value of v/I is called reactance. In Reactance There are 2 cases (1) If inductor in connected then in this case reactance is called inductive reactance, and its value in scalar form XL = ѡL, and in vector form XL=JѡL Where ѡ=2Πf. Here If frequency is increased then the value of wL is also increased. (2) If Capacitor is connected then the Reactance is called Capacitive Reactance and it is denoted by (scalar form) Xc = In vector form Where If frequency (f) is increased then value of Xc is decreased. ie ω inversly proportional to 2Πf. ♦ Impedance – If Any circuit consist Resistance -Inductor. Or Resistance - Capacitor, Or Resistance-inductor-Capacitor. Then the value of v/I is called Impedance. It is denoted by If Resistor(R) and Inductor(L) connected –The value of Impedance (scaler form) In vector form Z= R+jωL If Resistor (R) and Capacitor(C) connected - Then Impedance And In vector form impedance If Resistor (R) , Inductor (L) capacitor (C) Connected - Then Impedance In vector form Phasor Diagram of Impedance Unit Impedance - Ω Reactance - Ω Resistance - Ω Download What is impedance .pdf also read What is 555 timer What is NOT Gate Logic