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Showing posts from May, 2021

2:1 Multiplexer in Digital Electronics

- May 31, 2021

2:1 Multiplexer in Digital Electronics 2:1 Multiplexer A 2-to-1 multiplexer consists of two inputs Do and D1 and one select line S and one output Y. Depends on the select signal, the output is connected to either of the inputs. The block diagram of 2:1 multiplexer The mux will be enabled if enable(E) is activated. After enabling if the select line is low, then the output will be switched to D1 input. The boolean expression for the output becomes Do = when S=0 and output is D1 when S=1. Boolean expression for 2:1 multiplexer Y = Do S' + D1 S The logic circuit of 2:1 multiplexer can be implemented by using logic gates. It consists of two AND gates, one Not gate and one or gate. When the select line, S=0 the output of the lower AND gate is zero, but the Upper AND gate is Do. Thus the output generated by OR gate is equal to Do.

R-S Latch

- May 29, 2021

R-S latch R-S Latch Latchs is a basic building element in sequential circuits. Latches do not have clock signal, that is, they are asynchronous sequential circuits Latches are made up of static gates and are bi-stable i.e. it has two stable states and can switch between these states. Latches will have a feedback path from the output. Thus they change their output at any instant using the previous and present states of the signals R-S latch bloack diagram Where S=SET Input R=RESET Input Q=Output Qbar=Complemented Output RS latch implemented using NOR gates and we can store either a 0 ar a 1 in this circuit depending upon the vlaue of R and S When R=0, S=0 we don't have a change in the output in the circuit. Hence Q and Qbar remains in the pre

Direct Coupled CE Amplifier

- May 27, 2021

Direct Coupled CE Amplifier Direct Coupled CE amplifier Direct Coupled CE amplifier Direct Coupled amplifier using transistors. The ouput signal of first stage is directly connected to the input of the next stage. This direct couplig allows the quiescent d.c. Collector current of first stage to pass through base of the next stage, affecting its biasing conditions. Due to absence of RC components, its low frequency response is good but at higher frequencies shunting capacitors such as stray capacitances reduse the gain of the amplifier The transistor parameter such as Vbe and β change with temperature causing the collector current and voltage to change. Because of direct coupling these changes appear at the base of the next stage, and hence in the output. Such an unwanted change in the output is called Drift and it is serious problem in the direct Coupled amplifiers.

R-C Phase Shift Oscillator using Op-Amp

- May 26, 2021

R-C Phase Shift Oscillator using Op-Amp R-C Phase Shift Oscillator Using Op-Amp R-C phase shift oscillator using op-amp uses in inverting amplifier mode. Thus it introduce the phase shift of 180* between input and output The feedback network consists of 3 RC sections each producing 60* phase shift RC Phase Shift oscillator using op-amp The output of amplifer is given to feedback network. The output of feedback network drives the amplifier and 180* due to 3 RC section, thus 360*. This satisfies the required condition for positive feedback and circuit works as an oscillator. The gain of the op-amp |A|=> to satisfy the magnitude condition hence gain of the feedback network is β=1/29 so that |Aβ|=1 Thus Barkhausen criterion is satisfied and the circuit works as an oscillator. The freque

R-C Phase shift Oscillator

- May 25, 2021

R-C Phase shift Oscillator R-C Phase shift Oscillator RC phase shift oscillator basically consists of an amplifier and a feedback network consisting of resistors and capacitors arranged in ladder fashion. Hence such an oscillator is also called ladder type RC phase shift oscillator The basic RC circuit which is used in the feedback network of oscillator The total impedence of the circuit is, Z = R - j Xc = R - j[1/2πfc] Ω = |Z| ∠-φ Ω In such a RC circuit, current I leads input voltage Vi by angle φ where the angle φ is decided by the components R and C which is given by The drop Vr is in phase with current I while the drop Vc lags current I by 90* i.e. I leads Vc by 90*. Phasor Diagram Such 3 R-C sections are used, each contributing 60* phase shift hence the total phase shift co

Barkhausen Criterion

- May 24, 2021

Barkhausen Criterion Barkhausen Criterion Consider a basic inverting amplifier with an open loop gain A. As basic amplifier is inverting, it produces a phse shift of 180* between input and output. The feedback network attenuation factor β is less than unity. Now the input Vi applies to the amplifier is to be derived from its output Vo using feedback network. But the feedback must be positive i.e. the voltage derived from output using feedback network must be in phase with Vi. Thus the feedback network must introduce a phase shift of 180* while feeding back the voltage from output to input. This ensures positive feedback. The arrangement shown Consider a fictitions voltage Vi applied at the input of the amplifier. Hence we get, Vo = A Vi

Electronic Oscillator Division Types

- May 23, 2021

Electronic oscillator division types Electronic oscillator division types What is the oscillator ? An oscillator a circuit which produces a continous, repeated, alternating waveform without any input. Oscillators basically convert unidirectional current flow from a DC source into an alternating waveform which is of the desired frequency, as decided by its circuit components. There are many types of oscillator are there but more uses oscillator are Crystal Oscillator RC Oscillator LC Oscillator 1.Crystal Oscillator If the mechanical force is applied in such a way to force the crystal to vibrate, the a.c voltage get generated across it. Conversely, if the crystal is subjected to a.c voltage, it vibrates causing mechanical distortion in the crystal shape. Application of Crystal Oscillator We can use this crystal in Hartley Oscillator circuit Colpitt's Oscillator Circui

Zener Diode as Regulator

- May 22, 2021

Line Regulation with Zener Regulator Line Regulation with Zener Regulator Zener regulator under varying input voltage condition It can be seen the input is Vo=Vzis constant IL = Vo/Rl = Vz/Rl = constant And I = Iz+IL Now If Vin increases, than the total current I increases. But IL is constant as Vz is constant as Vz in constant. Hence the current Iz increases to keep IL constant But as long as Iz is between Izmin and Izmax, the Vz i.e output voltage Vo is constant Thus the changes in input voltage get compensated and output is maintained constant. Similarly if Vin decreases, than current I decreases. But to keep IL constant, Iz decreases. As long as Iz is between Izmax and Izmin the output voltage remains constant. the maximum power dissipation for the zener diode is fixed and given by Pd = VzIz max

Voltage Fallower

- May 20, 2021

Voltage Fallower Op-Amp as Voltage Fallower A circuit in which the output fallows the input voltage is called voltage fallower circuit The voltage fallower circuit using op-amp The node B is at potential Vin Now node A is also at the same potential as B i.e according to the same concept of virtual ground Va = Vb =Vin Now node A is directly connected to the ootput. Hence we can write, Vo = Va Vo = Vin For this circuit, the voltage gain is unity. Thus the output voltage Vo is equal to the input voltage Vin. If Vin increses, Vo also increases. If Vin decreases also Vo decreases. Thus output fallowes the input hence the circuit is called voltage fallower circuit. It also called source fallower, unity gain amplifier, buffer amplifier or isolation amplifier the input and output waveforms

Zero Crossing Detector

- May 19, 2021

Zero Crossing Detector Op-Amp as Zero Crossing Detector The basic non-inverting comparator can be used as a zero crossing detector This circuit tells wether the input siganl is greater than or less than zero and indicates the zero crossing points of the input A typical circuit for such a detector It is a non-inverting comparator circuit with Vref=0V. During the positive half cycle, the input voltage is positive i.e above the reference voltage. Hence voltage is +Vsat During negative half cycle, the input Vin is negative, i.e below the references voltage. The output voltage is than -Vsat. Thus the output voltage switches between +Vsat and -Vsat whenever the input signal crosses the zero level. Thus the output indicates the zero crossing of the input by changing the state of the output waveforms we realize that zero crossing detector can be used as a sine to square wave converter

Wien Bridge Oscillator

- May 18, 2021

Wien Bridge Oscillator Wien Bridge Oscillator A basic wien bridge and an amplifier The output of the amplifier is applied between the teriminals 1 and 3, which is the input to the feedback network While the amplifier input is supplied from the diagonal terminals 2 and 4, which is the output from the feedback network Thus amplifier supplies its own input through the wien bridge as a feedback network The 2 arms of the bridge, namely R1,C1 in series and R2,C2 in parallel are called frequency sensitive arms. This is because the camponents of these two ars deside the frequency of the oscillator. Such a feedback network is called lead-lag network. This is because at very low frequencies it acts like a lead while at very high frequencies it acts like lag network

R-C Phase Shift Oscillator

- May 17, 2021

R-C Phase Shift Oscillator using Op-Amp R-C Phase Shift Oscillator using Op-Amp R-C phase shift oscillator using op-amp uses in inverting amplifier mode. Thus it introduces the phase shift of 180* between input and output. The feedback network consists of 3 RC sections each producing 60* phase shift. Such a RC phase shift oscillator using op-amp the output of amplifier is given to feedback network The output of feedback network drives the amplifer. The total phase shift around a loop is 180* of amplifier and due to 3 RC section, thus 360* this satisfies the required condition for positive feedback and circuits works as an oscillator The gain of the op-amp|A|>=29 to satisfy the magnitude condition hence gain of feedback network is β=1/29 so that |Aβ|=1 Thus Barkhausen criteron is satisfied and the circuit works as an oscillator the frequency of oscillator f=1/2π√6 RC Hz

Crystal Oscillator

- May 16, 2021

Crystal Oscillator The cryatals are either naturally occuring or synthetically manufuctured, exhibiting the piezoelectric effect means under the influence of the mechanical pressure, the voltage gets generated across the opposite faces of the crystal Crystal If the mechanical force is applied in such a way to force the crystal to vibrate, the a.c voltage get generated across it. Conversely, if the crystal is subjected to a.c voltage, it vibrates causing mechanical distortion in the crystal shape. Every crystal has its own resonating frequency depending on its cut. So under the influence of the mechanical vibrations, the crystal generates an electrical signal of very constant frequency. The crystal has a greater stability in holding the constant frequency A crystal oscillator is basically a tuned-circuit oscillator using a piezoelectric crystal as its resonant tank circuit. The crystal oscillator are preferred when grea

Oscillator

- May 15, 2021

Piersce Crystal Oscillator Piersce Crystal Oscillator Thw colpitt's oscillator can be modified by by using the crystal to behave as an inductor. The circuit is called Pierce Crystal Oscillator. The crystal behaves as an inductor for a frequency slightly higher than the series resonance frequency Fs The two capacitors C1,C2 required in the tank circuit along with a crystal as an inductor are used, as htey are used in Colpitt's oscillator. As only inductor gets replaced by the crystal, which behaves as an inductor, the basic working principle of pierce crystal oscillator is same as that of colpitt's oscillator The practical transistoriced pierce crystal oscillator The resistances R1,R2,Re provide d.c bias while the capacitor Ce is emitter bypass capacitor. RFC (Radio Frequency Choke) provides isolation between a.c and d.c operation. Cc1 and Cc2 are the coupling capacitor. The resulting circuit frequency is the

Miller Crystal Oscillator

- May 14, 2021

Miller Crystal Oscillator Miller Crystal Oscillator Similar to modifications in Colpitt's oscillator, the Hartley oscillator circuit can be modified, to get Miller crystal Oscillator In Hartley oscillator circuit, two inductors and one capacitor is required in the tank circuit. One inductor is replaced by the crystal which acts as an inductor for the frequencies slightly greater then the series resonant frequency. The tuned circuit of L1 and C is offtuned to behave as an inductor i.e. L1. The crystal behaves as other inductance L2 between base and ground. the Internal capacitance of the transistor acts as a capacitor required to fullfill the elements of the tank circuit The crystal decides the operating frequency of the oscillator.

Colpitts Oscillator

- May 13, 2021

Colpitts oscillator Colpitts oscillator The LC tank circuit uses two capacitive reactance and one inductive reactance. X1=X2=C and X3=L The amplifier stage uses an active as a transistor in common emmitterconfiguration. The R1 and R2 are the biasing resistances. The RFC is the radio freqency chock. Its reactance value is very high for high frequencies, hence it can be treated as open circuit for a.c. While for d.c conditions, the reactance is zero hence causes no problem for d.c capacitors and biasing. Re is also a biasing circuit resistance and CE is the emitter bypass capacitor.Cc1 and Cc2 are the coupling capacitors The common emitter amplifier causes a phase shift of 180*, while the tank circuit adds further 180* phase shift. Thus the total phase shift around a loop is 360* which is necessary to satisfy Barkhausen condition . To satisfy Aβ=>1, it is necessary that hfe of the transistor used in the ampli

Hartley Oscillators

- May 12, 2021

Hartley Oscillators Hartley Oscillator Depending upon this, LC oscillators are classified as Hartley Oscillator Colpitt's Oscillator Hartly oscillator has in the feedback LC tank Two Inductance and On capacitance Colitt's oscillator has in the feedback LC tank is two capacitance and one inductance Now we understanding about Hartley oscillator The LC tank circuit of Hartley oscillator uses two inductance reactances and one capacitive reactance X1=X2=L and X3=C The hartley oscillator using transistor The amplifier stage uses an active device as a transistor in common emittr configuration The resistances R1 and R2 are the biasing resistances. The RFC is the radio chocke. Its reactance value is very high frequencies, hence it can be treated as open circuit for a.c. While for d.c conditions, the reactance is zero hence causes no problem for d.c capacitors and biasing.Hence due to

LC Oscillators

- May 11, 2021

General Form Of LC oscillators The general form of lc oscillator using amplifier The feedback network uses three impedences which are practically pure reactances. i.e. Z1=jX1,Z2=jX2,Z3=jX3 Amplifier provide the phase shift of 180* while the feedback network provides the additional 180* to compleate 360* phase shift around a loop To satisfy Aβ >=1, it is observed thet the X1 and X2 must be of same type while X3 must be opposite. Thus if X1 and X2 are inductive the x3 must be capacitive while if X1 and X2 are capacitive then X3 must be inductive. Hence in LC oscillators, the feedback network consists of two inductors and one capacitor or two capacitors and one inductor.

Full Wave Rectifier Using Center Tap Transformer

- May 10, 2021

Full Wave Rectifier Using Center Tap Transformer Full wave rectifier The full wave rectifier conducts during positive and negative half cycle of input a.c supply In order to rectify both the half cyles of a.c input, two diodes are used in this circuit The diode feed a common load Rl with the help of a center tap transformer The a.c voltage is applied through a suitable power transformer with proper turns ratio The full wave rectifier circuit Opearation of the circuit consider the positive half cycle of the a.c input voltage in which terminal(A) is posive terminal (B) negative due to center tap transformer The diode D1 will be forward biased and hence will conduct; while diode D2 will be reverse biased and will act as open circuit and will not conduct. The diode D1 supplies the load current, i.e. il=id1 In next half cycle of a.c voltage, polarity reverse and terminal (A) becomes negative and t

Half wave Rectifier

- May 09, 2021

Recifier Circuit Half wave rectifier Circuit Diagram The rectifier circuit cosists of resistive load, rectifying element, i.e. p-n junction diode and the source of a.c voltage, all connected in series To ontain the desired d.c voltage across the load, the a.c voltage is applied to rectifier circuit using suitable step-down, step-up transformer, mostly a step-down one with necessary turns ratio. Operation of the Circuit During positive half cyle of input a.c voltage, terminal (A) becomes positive with respect to terminal (B). The diode is forward biased and the current flows in the clockwise direction. This current is also flowing through the load resistance RL hence denoted as IL(load current). During negative half cycle when terminal (A) is negative with respect to terminal (B), diode becomes reverse biased. Hence no current flows. Thus the circuit, which is also the load current, is in the form of ha

Regulated power supply

- May 08, 2021

Block Schmatic Regualted powe supply D.C Power Supplay Stages The block diagram of d.c power supply A typical d.c power supply consists of varies stages. The block diagram of d.c power supply consisting of varies circuit. 1.Transformer The a.c voltage(230v,50Hz) is connected to the primary of the transformer. The transformer steps down the a.c voltage, to required for the desired d.c voltage output. Thus, with suitable turns ratio we get desired a.c voltage 2.Rectifier Circuit The rectifier circuit converts this a.c voltage into a pulsating d.c voltage . A pulsating d,c voltage means a undirectional voltage containing large varying component called ripple in it 3.Filter circuit The filter circuit is used after a rectifier circuit, which reduses the ripple content in the pulsating d.c tries to make it smoother. Still then the filter output contains the some ripple. The voltage is called unregulated

Op-Amp as Non-Inverting Comparator

- May 07, 2021

Basic Non-Inverting Comparator Non-Inverting comparator The basic non-inverting comparator in this comparator, the input voltage is applied to the non-inverting terminal and no reference voltage is applied to other terminal So inverting terminal is grounded the input voltage is denoted as Vin while the voltage applied to other terminal with which Vin is compared in denoted as Vref In the basic comparator, Vref=0V In the non-inverting comparator, If Vin is greatr then Vref, Then output is +Vsat i.e. almost is equal to +Vcc while if Vin is less then Vref then output is -Vsat i.e. almost equal to -Vee As Vref=0V when Vin is positive then Vo=+Vsat, While when Vin is Negative then Vo=-Vsat This is because, as open loop gain op-amp is very very high even for verry small Vin the op-amp output saturates The input and output waveforms for a basic non-inverting comparator, for sinusoida

Oscillators

- May 06, 2021

Classification of oscillators Classification of oscillators The oscillators are classified based on the nature of the output of the waveforms, the parameters used, the range of the frequency etc The varies ways in which oscillators are classified as: 1.Based on the Output Waveforms Under this, the oscillators are classified as sinusoidal and nonsinusoidal oscillators The sinusoidal oscillator generates purely sinusoidal waveforms at the output While nonsinusoidal oscillator generates at the output squre wave, triangular wave,sawtooth etc. The basic block diagram of the oscillator circuit 2.Based on the circuit components The oscillators using the components rsistance(R) and capacitance(C), are called RC oscillators While oscillators using the components inductance(L) and capacitance(C) is called LC osicllators Some oscillators are using the crystal used are called crystel oscilla

Op-Amp as Inverting Amplifier

- May 05, 2021

Inverting amplifier using op-amp Inverting Amplifier An amplifire which gives 180' phase different between input and output is called inverting amplifier The block diagram of inverting amplifier By the virtual ground concept the two input terminals are always at the same potential As node B is grounded and also node A is at ground potential, from virtual ground concept I=Vin-Va/R1=Vin/R1 (as Va=0)....................equation (1) The op-amp input current is always zero hence entire current flows through the feedback resister Rf from output side I=Va-V0/Rf=-V0/Rf (as Va=0)..........................equation (2) from equation 1 and 2 Vin/R1=-V0/Rf Av=-Rf/R1 -Rf/R1 is the gain of the amplitude while negative sine indicates that the polarity of the output is opposite of the input hence this called inverting amplifier inverting amplifier waveforms

Op-Amp Symbol and Terminals

- May 04, 2021

Op-Amp Op-Amp Symbol Terminals Basically op-amp symbol is triangle shape how the current flow through op-amp op-amp basically have 8 pins we use only five pins pin number 2 is the inverting terminal pin number 3 is non-inverting terminal pin number 4 is negative -15 volt input pin number 6 is the ouput singal pin pin number 7 is the +15 volt input When the input is applie to pin no:-2 that is inverting terminal, her the input and otput phase different between 180* When the input is applied to the pin:-3 thet is non-inverting terminal, Here there no phase difference between input and output op-amp has dual supply that is DC supply pin no:- positive supply 7 and negative supply 4.

Parallel Negative Clipper

- May 03, 2021

shunt or parallel clipper parallel negative clipper In this parallel negative clipper and positive clipper difference between the diode orientation in this paralle negative clipper have a diode and one resistance and another one is load resistance During positive half cycle the diode becomes reverse biased and entire current will flow through the load resistance When the diode is reverse biased the diode act as oprn switch or loop no current flows through the diode During negative half cycle the diode will be forward biased and entire curent will flow through the diode When the diode is forward biased and the diode act as a close switch or loop the entire current will flow through the diode input and output waveforms click here to follow me in instagram instagram

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