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Electronic Circuits – Rectifiers Whenever there arises the need to convert an AC to DC power, a rectifier circuit comes for the rescue. A simple PN junction diode acts as a rectifier. The forward biasing and reverse biasing conditions of the diode makes the rectification. Rectification An alternating current has the property to change its state continuously. This is understood by observing the sine wave by which an alternating current is indicated. It raises in its positive direction goes to a peak positive value, reduces from there to normal and again goes to negative portion and reaches the negative peak and again gets back to normal and goes on. During its journey in the formation of wave, we can observe that the wave goes in positive and negative directions. Actually it alters completely and hence the name alternating current. But during the process of rectification, this alternating current is changed into direct current DC. The wave which flows in both positive and negative direction till then, will get its direction restricted only to positive direction, when converted to DC. Hence the current is allowed to flow only in positive direction and resisted in negative direction, just as in the figure below. The circuit which does rectification is called as a Rectifier circuit. A diode is used as a rectifier, to construct a rectifier circuit. Types of Rectifier circuits There are two main types of rectifier circuits, depending upon their output. They are Half-wave Rectifier Full-wave Rectifier A Half-wave rectifier circuit rectifies only positive half cycles of the input supply whereas a Full-wave rectifier circuit rectifies both positive and negative half cycles of the input supply. Half-Wave Rectifier The name half-wave rectifier itself states that the rectification is done only for half of the cycle. The AC signal is given through an input transformer which steps up or down according to the usage. Mostly a step down transformer is used in rectifier circuits, so as to reduce the input voltage. The input signal given to the transformer is passed through a PN junction diode which acts as a rectifier. This diode converts the AC voltage into pulsating dc for only the positive half cycles of the input. A load resistor is connected at the end of the circuit. The figure below shows the circuit of a half wave rectifier. Working of a HWR TThe input signal is given to the transformer which reduces the voltage levels. The output from the transformer is given to the diode which acts as a rectifier. This diode gets ON (conducts) for positive half cycles of input signal. Hence a current flows in the circuit and there will be a voltage drop across the load resistor. The diode gets OFF (doesn’t conduct) for negative half cycles and hence the output for negative half cycles will be, $i_{D} = 0$ and $V_{o}=0$. Hence the output is present for positive half cycles of the input voltage only (neglecting the reverse leakage current). This output will be pulsating which is taken across the load resistor. Waveforms of a HWR The input and output waveforms are as shown in the following figure. Hence the output of a half wave rectifier is a pulsating dc. Let us try to analyze the above circuit by understanding few values which are obtained from the output of half wave rectifier. Analysis of Half-Wave Rectifier To analyze a half-wave rectifier circuit, let us consider the equation of input voltage. $$v_{i}=V_{m} sin omega t$$ $V_{m}$ is the maximum value of supply voltage. Let us assume that the diode is ideal. The resistance in the forward direction, i.e., in the ON state is $R_f$. The resistance in the reverse direction, i.e., in the OFF state is $R_r$. The current i in the diode or the load resistor $R_L$ is given by $i=I_m sin omega t quad forquad 0leq omega tleq 2 pi$ $ i=0 quadquadquadquad for quad pileq omega tleq 2 pi$ Where $$I_m= frac{V_m}{R_f+R_L}$$ DC Output Current The average current $I_{dc}$ is given by $$I_{dc}=frac{1}{2 pi}int_{0}^{2 pi} i :dleft ( omega t right )$$ $$=frac{1}{2 pi}left [ int_{0}^{pi}I_m sin omega t :dleft ( omega t right )+int_{0}^{2 pi}0: dleft ( omega t right )right ]$$ $$=frac{1}{2 pi}left [ I_mleft {-cos omega t right }_{0}^{pi} right ]$$ $$=frac{1}{2 pi}left [ I_mleft { +1-left ( -1 right ) right } right ]=frac{I_m}{pi}=0.318 I_m$$ Substituting the value of $I_m$, we get $$I_{dc}=frac{V_m}{pileft ( R_f+R_L right )}$$ If $R_L >> R_f$, then $$I_{dc}=frac{V_m}{pi R_L}=0.318 frac{V_m}{R_L}$$ DC Output Voltage The DC output voltage is given by $$ V_{dc}=I_{dc}times R_L=frac{I_m}{pi}times R_L$$ $$=frac{V_mtimes R_L}{pileft (R_f+R_L right )}=frac{V_m}{pileft { 1+left ( R_f/R_L right ) right }}$$ If $R_L>>R_f$, then $$V_{dc}=frac{V_m}{pi}=0.318 V_m$$ RMS Current and Voltage The value of RMS current is given by $$I_{rms}=left [ frac{1}{2 pi}int_{0}^{2pi} i^{2} dleft ( omega t right )right ]^{frac{1}{2}}$$ $$I_{rms}=left [ frac{1}{2 pi}int_{0}^{2pi}I_{m}^{2} sin^{2}omega t :dleft (omega t right ) +frac{1}{2pi}int_{pi}^{2pi} 0 :dleft ( omega t right )right ]^{frac{1}{2}}$$ $$=left [ frac{I_{m}^{2}}{2 pi}int_{0}^{pi}left ( frac{1-cos 2 omega t}{2} right )dleft ( omega t right ) right ]^{frac{1}{2}}$$ $$=left [ frac{I_{m}^{2}}{4 pi}left { left ( omega t right )-frac{sin 2 omega t}{2} right }_{0}^{pi}right ]^{frac{1}{2}}$$ $$=left [ frac{I_{m}^{2}}{4 pi}left { pi – 0 – frac{sin 2 pi}{2}+ sin 0 right } right ]^{frac{1}{2}}$$ $$=left [ frac{I_{m}^{2}}{4 pi} right ]^{frac{1}{2}}=frac{I_m}{2}$$ $$=frac{V_m}{2left ( R_f+R_L right )}$$ RMS voltage across the load is $$V_{rms}=I_{rms} times R_L= frac{V_m times R_L}{2left ( R_f+R_L right )}$$ $$=frac{V_m}{2left { 1+left ( R_f/R_L right ) right }}$$ If $R_L>>R_f$, then $$V_{rms}=frac{V_m}{2}$$ Rectifier Efficiency Any circuit needs to be efficient in its working for a better output. To calculate the efficiency of a half wave rectifier, the ratio of the output power to the input power has to be considered. The rectifier efficiency is defined as $$eta =frac{d.c.power:: delivered :: to :: the :: load}{a.c.input :: power::from::transformer::secondary}=frac{P_{ac}}{P_{dc}}$$ Now $$P_{dc}=left ( {I_{dc}} right )^2 times R_L=frac{I_m R_L}{pi^2}$$ Further $$P_{ac}=P_a+P_r$$ Where $P_a = power :dissipated :at :the :junction :of :diode$ $$=I_{rms}^{2}times R_f=frac{I_{m}^{2}}{4}times R_f$$ And $$P_r = power :dissipated :in
Electronic Circuits – Quick Guide Electronic Circuits – Introduction In Electronics, we have different components that serve different purposes. There are various elements which are used in many types of circuits depending on the applications. Electronic Components Similar to a brick that constructs a wall, a component is the basic brick of a circuit. A Component is a basic element that contributes for the development of an idea into a circuit for execution. Each component has a few basic properties and the component behaves accordingly. It depends on the motto of the developer to use them for the construction of the intended circuit. The following image shows a few examples of electronic components that are used in different electronic circuits. Just to gather an idea, let us look at the types of Components. They can either be Active Components or Passive Components. Active Components Active Components are those which conduct upon providing some external energy. Active Components produce energy in the form of voltage or current. Examples − Diodes, Transistors, Transformers, etc. Passive Components Passive components are those which start their operation once they are connected. No external energy is needed for their operation. Passive components store and maintain energy in the form of voltage or current. Examples − Resistors, Capacitors, Inductors, etc. We also have another classification as Linear and Non-Linear elements. Linear Components Linear elements or components are the ones that have linear relationship between current and voltage. The parameters of linear elements are not changed with respect to current and voltage. Examples − Diodes, Transistors, Transformers, etc. Non-linear Components Non-linear elements or components are the ones that have a non-linear relationship between current and voltage. The parameters of non-linear elements are changed with respect to current and voltage. Examples − Resistors, Capacitors, Inductors, etc. These are the components intended for various purposes, which altogether can perform a preferred task for which they are built. Such a combination of different components is known as a Circuit. Electronic Circuits A certain number of components when connected on a purpose in a specific fashion makes a circuit. A circuit is a network of different components. There are different types of circuits. The following image shows different types of electronic circuits. It shows Printed Circuit Boards which are a group of electronic circuits connected on a board. Electronic circuits can be grouped under different categories depending upon their operation, connection, structure, etc. Let’s discuss more about the types of Electronic Circuits. Active Circuit A circuit that is build using Active components is called as Active Circuit. It usually contains a power source from which the circuit extracts more power and delivers it to the load. Additional Power is added to the output and hence output power is always greater than the input power applied. The power gain will always be greater than unity. Passive Circuit A circuit that is build using Passive components is called as Passive Circuit. Even if it contains a power source, the circuit does not extract any power. Additional Power is not added to the output and hence output power is always less than the input power applied. The power gain will always be less than unity. Electronic circuits can also be classified as Analog, Digital, or Mixed. Analog Circuit An analog circuit can be one which has linear components in it. Hence it is a linear circuit. An analog circuit has analog signal inputs which are continuous range of voltages. Digital Circuit A digital circuit can be one which has non-linear components in it. Hence it is a non-linear circuit. It can process digital signals only. A digital circuit has digital signal inputs which are discrete values. Mixed Signal Circuit A mixed signal circuit can be one which has both linear and non-linear components in it. Hence it is called as a mixed signal circuit. These circuits consist of analog circuitry along with microprocessors to process the input. Depending upon the type of connection, circuits can be classified as either Series Circuit or Parallel Circuit. A Series Circuit is one which is connected in series and a parallel circuit is one which has its components connected in parallel. Now that we have a basic idea about electronic components, let us move on and discuss their purpose which will help us build better circuits for different applications. Whatever might be the purpose of an electronic circuit (to process, to send, to receive, to analyze), the process is carried out in the form of signals. In the next chapter, we will discuss the signals and the type of signals present in electronic circuits. Electronic Circuits – Signals A Signal can be understood as “a representation that gives some information about the data present at the source from which it is produced.” This is usually time varying. Hence, a signal can be a source of energy which transmits some information. This can easily be represented on a graph. Examples An alarm gives a signal that it’s time. A cooker whistle confirms that the food is cooked. A red light signals some danger. A traffic signal indicates your move. A phone rings signaling a call for you. A signal can be of any type that conveys some information. This signal produced from an electronic equipment, is called as Electronic Signal or Electrical Signal. These are generally time variants. Types of Signals Signals can be classified either as Analog or Digital, depending upon their characteristics. Analog and Digital signals can be further classified, as shown in the following image. Analog Signal A continuous time-varying signal, which represents a time-varying quantity, can be termed as an Analog Signal. This signal keeps on varying with respect to time, according to the instantaneous values of the quantity, which represents it. Digital Signal A signal which is discrete in nature or which is non-continuous in form can be termed as a Digital signal. This signal has individual values, denoted separately, which are not based on previous values, as if they are derived at that
Limiter and Voltage Multiplier Along with the wave shaping circuits such as clippers and clampers, diodes are used to construct other circuits such as limiters and voltage multipliers, which we shall discuss in this chapter. Diodes also have another important application known as rectifiers, which will be discussed later. Limiters Another name which we often come across while going through these clippers and clampers is the limiter circuit. A limiter circuit can be understood as the one which limits the output voltage from exceeding a pre-determined value. This is more or less a clipper circuit which does not allow the specified value of the signal to exceed. Actually clipping can be termed as an extreme extent of limiting. Hence limiting can be understood as a smooth clipping. The following image shows some examples of limiter circuits − The performance of a limiter circuit can be understood from its transfer characteristic curve. An example for such a curve is as follows. The lower and upper limits are specified in the graph which indicate the limiter characteristics. The output voltage for such a graph can be understood as $$V_{0}= L_{-},KV_{i},L_{+}$$ Where $$L_{-}=V_{i}leq frac{L_{-}}{k}$$ $$KV_{i}=frac{L_{-}}{k} $$L_{+}=V_{i}geq frac{L_{+}}{K}$$ Types of Limiters There are few types of limiters such as Unipolar Limiter − This circuit limits the signal in one way. Bipolar Limiter − This circuit limits the signal in two way. Soft Limiter − The output may change in this circuit for even a slight change in the input. Hard Limiter − The output will not easily change with the change in input signal. Single Limiter − This circuit employs one diode for limiting. Double Limiter − This circuit employs two diodes for limiting. Voltage Multipliers There are applications where the voltage needs to be multiplied in some cases. This can be done easily with the help of a simple circuit using diodes and capacitors. The voltage if doubled, such a circuit is called as a Voltage Doubler. This can be extended to make a Voltage Tripler or a Voltage Quadrupler or so on to obtain high DC voltages. To get a better understanding, let us consider a circuit that multiplies the voltage by a factor of 2. This circuit can be called as a Voltage Doubler. The following figure shows the circuit of a voltage doubler. The input voltage applied will be an AC signal which is in the form of a sine wave as shown in the figure below. Working The voltage multiplier circuit can be understood by analyzing each half cycle of the input signal. Each cycle makes the diodes and the capacitors work in different fashion. Let us try to understand this. During the first positive half cycle − When the input signal is applied, the capacitor $C_{1}$ is charged and the diode $D_{1}$ is forward biased. While the diode $D_{2}$ is reverse biased and the capacitor $C_{2}$ doesn’t get any charge. This makes the output $V_{0}$ to be $V_{m}$ This can be understood from the following figure. Hence, during 0 to $pi$, the output voltage produced will be $V_{max}$. The capacitor $C_{1}$ gets charged through the forward biased diode $D_{1}$ to give the output, while $C_{2}$ doesn’t charge. This voltage appears at the output. During the negative half cycle − After that, when the negative half cycle arrives, the diode $D_{1}$ gets reverse biased and the diode $D_{2}$ gets forward biased. The diode $D_{2}$ gets the charge through the capacitor $C_{2}$ which gets charged during this process. The current then flows through the capacitor $C_{1}$ which discharges. It can be understood from the following figure. Hence during $pi$ to $2pi$, the voltage across the capacitor $C_{2}$ will be $V_{max}$. While the capacitor $C_{1}$ which is fully charged, tends to discharge. Now the voltages from both the capacitors together appear at the output, which is $2V_{max}$. So, the output voltage $V_{0}$ during this cycle is $2V_{max}$ During the next positive half cycle − The capacitor $C_{1}$ gets charged from the supply and the diode $D_{1}$ gets forward biased. The capacitor $C_{2}$ holds the charge as it will not find a way to discharge and the diode $D_{2}$ gets reverse biased. Now, the output voltage $V_{0}$ of this cycle gets the voltages from both the capacitors that together appear at the output, which is $2V_{max}$. During the next negative half cycle − The next negative half cycle makes the capacitor $C_{1}$ to again discharge from its full charge and the diode $D_{1}$ to reverse bias while $D_{2}$ forward and capacitor $C_{2}$ to charge further to maintain its voltage. Now, the output voltage $V_{0}$ of this cycle gets the voltages from both the capacitors that together appear at the output, which is $2V_{max}$. Hence, the output voltage $V_{0}$ is maintained to be $2V_{max}$ throughout its operation, which makes the circuit a voltage doubler. Voltage multipliers are mostly used where high DC voltages are required. For example, cathode ray tubes and computer display. Voltage Divider While diodes are used to multiply the voltage, a set of series resistors can be made into a small network to divide the voltage. Such networks are called as Voltage Divider networks. Voltage divider is a circuit which turns a larger voltage into a smaller one. This is done using resistors connected in series. The output will be a fraction of the input. The output voltage depends upon the resistance of the load it drives. Let us try to know how a voltage divider circuit works. The figure below is an example of a simple voltage divider network. If we try to draw an expression for output voltage, $$V_{i}=ileft ( R_{1}+R_{2} right )$$ $$i=frac{V-{i}}{left ( R_{1}+R_{2} right )}$$ $$V_{0}=i :R_{2}rightarrow :i:=frac{V_{0}}{R_{2}}$$ Comparing both, $$frac{V_{0}}{R_{2}}=frac{V_{i}}{left ( R_1 + R_{2} right )}$$ $$V_{0}=frac{V_{i}}{left ( R_1 + R_{2} right )}R_{2}$$ This is the expression to obtain the value of output voltage. Hence the output voltage is divided depending upon the resistance values of the resistors in the network. More resistors are added to have different fractions of different output voltages.
Discuss Electronic Circuits This tutorial explains the very basic circuits in Electronics and Communications. The circuits mentioned in this tutorial are mostly related to the applications of diodes. The components mentioned in have their applications seen here. Almost all the important diode circuits are covered in this tutorial. Learning working make money
Electronic Circuits Tutorial Job Search This tutorial explains the very basic circuits in Electronics and Communications. The circuits mentioned in this tutorial are mostly related to the applications of diodes. The components mentioned in have their applications seen here. Almost all the important diode circuits are covered in this tutorial. Audience This tutorial is intended for beginners in the field of Electronics and Communications and hence, it would be useful for most students. It has been designed keeping in mind the requirements of beginners who are interested in learning the functionalities of basic circuits used in Electronics and Communication. Prerequisites The readers should have elementary knowledge regarding electronic components to make the most of this tutorial, however it is not a necessity. If you want to refresh your knowledge on the construction, working, and applications of electronic components, then please go through our first. Learning working make money
Electronic Circuits – Filters The power supply block diagram clearly explains that a filter circuit is needed after the rectifier circuit. A rectifier helps in converting a pulsating alternating current to direct current, which flows only in one direction. Till now, we have seen different types of rectifier circuits. The outputs of all these rectifier circuits contains some ripple factor. We have also observed that the ripple factor of a half wave rectifier is greater than that of a full wave rectifier. Why Do We Need Filters? The ripple in the signal denotes the presence of some AC component. This ac component has to be completely removed in order to get pure dc output. So, we need a circuit that smoothens the rectified output into a pure dc signal. A filter circuit is one which removes the ac component present in the rectified output and allows the dc component to reach the load. The following figure shows the functionality of a filter circuit. A filter circuit is constructed using two main components, inductor and capacitor. We have already studied in Basic Electronics tutorial that An inductor allows dc and blocks ac. A capacitor allows ac and blocks dc. Let us try to construct a few filters, using these two components. Series Inductor Filter As an inductor allows dc and blocks ac, a filter called Series Inductor Filter can be constructed by connecting the inductor in series, between the rectifier and the load. The figure below shows the circuit of a series inductor filter. The rectified output when passed through this filter, the inductor blocks the ac components that are present in the signal, in order to provide a pure dc. This is a simple primary filter. Shunt Capacitor Filter As a capacitor allows ac through it and blocks dc, a filter called Shunt Capacitor Filter can be constructed using a capacitor, connected in shunt, as shown in the following figure. The rectified output when passed through this filter, the ac components present in the signal are grounded through the capacitor which allows ac components. The remaining dc components present in the signal are collected at the output. The above filter types discussed are constructed using an inductor or a capacitor. Now, let’s try to use both of them to make a better filter. These are combinational filters. L-C Filter A filter circuit can be constructed using both inductor and capacitor in order to obtain a better output where the efficiencies of both inductor and capacitor can be used. The figure below shows the circuit diagram of a LC filter. The rectified output when given to this circuit, the inductor allows dc components to pass through it, blocking the ac components in the signal. Now, from that signal, few more ac components if any present are grounded so that we get a pure dc output. This filter is also called as a Choke Input Filter as the input signal first enters the inductor. The output of this filter is a better one than the previous ones. Π- Filter (Pi filter) This is another type of filter circuit which is very commonly used. It has capacitor at its input and hence it is also called as a Capacitor Input Filter. Here, two capacitors and one inductor are connected in the form of π shaped network. A capacitor in parallel, then an inductor in series, followed by another capacitor in parallel makes this circuit. If needed, several identical sections can also be added to this, according to the requirement. The figure below shows a circuit for $pi$ filter (Pi-filter). Working of a Pi filter In this circuit, we have a capacitor in parallel, then an inductor in series, followed by another capacitor in parallel. Capacitor C1 − This filter capacitor offers high reactance to dc and low reactance to ac signal. After grounding the ac components present in the signal, the signal passes to the inductor for further filtration. Inductor L − This inductor offers low reactance to dc components, while blocking the ac components if any got managed to pass, through the capacitor C1. Capacitor C2 − Now the signal is further smoothened using this capacitor so that it allows any ac component present in the signal, which the inductor has failed to block. Thus we, get the desired pure dc output at the load. Learning working make money
Electronic Circuits – Clamper Circuits A Clamper Circuit is a circuit that adds a DC level to an AC signal. Actually, the positive and negative peaks of the signals can be placed at desired levels using the clamping circuits. As the DC level gets shifted, a clamper circuit is called as a Level Shifter. Clamper circuits consist of energy storage elements like capacitors. A simple clamper circuit comprises of a capacitor, a diode, a resistor and a dc battery if required. Clamper Circuit A Clamper circuit can be defined as the circuit that consists of a diode, a resistor and a capacitor that shifts the waveform to a desired DC level without changing the actual appearance of the applied signal. In order to maintain the time period of the wave form, the tau must be greater than, half the time period (discharging time of the capacitor should be slow.) $$tau = Rc$$ Where R is the resistance of the resistor employed C is the capacitance of the capacitor used The time constant of charge and discharge of the capacitor determines the output of a clamper circuit. In a clamper circuit, a vertical shift of upward or downward takes place in the output waveform with respect to the input signal. The load resistor and the capacitor affect the waveform. So, the discharging time of the capacitor should be large enough. The DC component present in the input is rejected when a capacitor coupled network is used (as a capacitor blocks dc). Hence when dc needs to be restored, clamping circuit is used. Types of Clampers There are few types of clamper circuits, such as Positive Clamper Positive clamper with positive $V_r$ Positive clamper with negative $V_r$ Negative Clamper Negative clamper with positive $V_{r}$ Negative clamper with negative $V_{r}$ Let us go through them in detail. Positive Clamper Circuit A Clamping circuit restores the DC level. When a negative peak of the signal is raised above to the zero level, then the signal is said to be positively clamped. A Positive Clamper circuit is one that consists of a diode, a resistor and a capacitor and that shifts the output signal to the positive portion of the input signal. The figure below explains the construction of a positive clamper circuit. Initially when the input is given, the capacitor is not yet charged and the diode is reverse biased. The output is not considered at this point of time. During the negative half cycle, at the peak value, the capacitor gets charged with negative on one plate and positive on the other. The capacitor is now charged to its peak value $V_{m}$. The diode is forward biased and conducts heavily. During the next positive half cycle, the capacitor is charged to positive Vm while the diode gets reverse biased and gets open circuited. The output of the circuit at this moment will be $$V_{0}=V_{i}+V_{m}$$ Hence the signal is positively clamped as shown in the above figure. The output signal changes according to the changes in the input, but shifts the level according to the charge on the capacitor, as it adds the input voltage. Positive Clamper with Positive Vr A Positive clamper circuit if biased with some positive reference voltage, that voltage will be added to the output to raise the clamped level. Using this, the circuit of the positive clamper with positive reference voltage is constructed as below. During the positive half cycle, the reference voltage is applied through the diode at the output and as the input voltage increases, the cathode voltage of the diode increase with respect to the anode voltage and hence it stops conducting. During the negative half cycle, the diode gets forward biased and starts conducting. The voltage across the capacitor and the reference voltage together maintain the output voltage level. Positive Clamper with Negative $V_{r}$ A Positive clamper circuit if biased with some negative reference voltage, that voltage will be added to the output to raise the clamped level. Using this, the circuit of the positive clamper with positive reference voltage is constructed as below. During the positive half cycle, the voltage across the capacitor and the reference voltage together maintain the output voltage level. During the negative half-cycle, the diode conducts when the cathode voltage gets less than the anode voltage. These changes make the output voltage as shown in the above figure. Negative Clamper A Negative Clamper circuit is one that consists of a diode, a resistor and a capacitor and that shifts the output signal to the negative portion of the input signal. The figure below explains the construction of a negative clamper circuit. During the positive half cycle, the capacitor gets charged to its peak value $v_{m}$. The diode is forward biased and conducts. During the negative half cycle, the diode gets reverse biased and gets open circuited. The output of the circuit at this moment will be $$V_{0}=V_{i}+V_{m}$$ Hence the signal is negatively clamped as shown in the above figure. The output signal changes according to the changes in the input, but shifts the level according to the charge on the capacitor, as it adds the input voltage. Negative clamper with positive Vr A Negative clamper circuit if biased with some positive reference voltage, that voltage will be added to the output to raise the clamped level. Using this, the circuit of the negative clamper with positive reference voltage is constructed as below. Though the output voltage is negatively clamped, a portion of the output waveform is raised to the positive level, as the applied reference voltage is positive. During the positive half-cycle, the diode conducts, but the output equals the positive reference voltage applied. During the negative half cycle, the diode acts as open circuited and the voltage across the capacitor forms the output. Negative Clamper with Negative Vr A Negative clamper circuit if biased with some negative reference voltage, that voltage will be added to the output to raise the clamped level. Using this, the circuit of the
Electronic Circuits – Linear Wave Shapping A Signal can also be called as a Wave. Every wave has a certain shape when it is represented in a graph. This shape can be of different types such as sinusoidal, square, triangular, etc. which vary with respect to time period or they may have some random shapes disregard of the time period. Types of Wave Shaping There are two main types of wave shaping. They are − Linear wave shaping Non-linear wave shaping Linear Wave Shaping Linear elements such as resistors, capacitors and inductors are employed to shape a signal in this linear wave shaping. A Sine wave input has a sine wave output and hence the nonsinusoidal inputs are more prominently used to understand the linear wave shaping. Filtering is the process of attenuating the unwanted signal or to reproduce the selected portions of the frequency components of a particular signal. Filters In the process of shaping a signal, if some portions of the signal are felt unwanted, they can be cut off using a Filter Circuit. A Filter is a circuit that can remove unwanted portions of a signal at its input. The process of reduction in the strength of the signal is also termed as Attenuation. We have few components which help us in filtering techniques. A Capacitor has the property to allow AC and to block DC An Inductor has the property to allow DC but blocks AC. Using these properties, these two components are especially used to block or allow AC or DC. The Filters can be designed depending upon these properties. We have four main types of filters − Low pass filter High pass filter Band pass filter Band stop filter Let us now discuss these types of filters in detail. Low Pass Filter A Filter circuit which allows a set of frequencies that are below a specified value can be termed as a Low pass filter. This filter passes the lower frequencies. The circuit diagram of a low pass filter using RC and RL are as shown below. The capacitor filter or RC filter and the inductor filter or RL filter both act as low pass filters. The RC filter − As the capacitor is placed in shunt, the AC it allows is grounded. This by passes all the high frequency components while allows DC at the output. The RL filter − As the inductor is placed in series, the DC is allowed to the output. The inductor blocks AC which is not allowed at the output. The symbol for a low pass filter (LPF) is as given below. Frequency Response The frequency response of a practical filter is as shown here under and the frequency response of an ideal LPF when the practical considerations of electronic components are not considered will be as follows. The cut off frequency for any filter is the critical frequency $f_{c}$ for which the filter is intended to attenuate (cut) the signal. An ideal filter has a perfect cut-off whereas a practical one has few limitations. The RLC Filter After knowing about the RC and RL filters, one may have an idea that it would be good to add these two circuits in order to have a better response. The following figure shows how the RLC circuit looks like. The signal at the input goes through the inductor which blocks AC and allows DC. Now, that output is again passed through the capacitor in shunt, which grounds the remaining AC component if any, present in the signal, allowing DC at the output. Thus we have a pure DC at the output. This is a better low pass circuit than both of them. High Pass Filter A Filter circuit which allows a set of frequencies that are above a specified value can be termed as a High pass filter. This filter passes the higher frequencies. The circuit diagram of a high pass filter using RC and RL are as shown below. The capacitor filter or RC filter and the inductor filter or RL filter both act as high pass filters. The RC Filter As the capacitor is placed in series, it blocks the DC components and allows the AC components to the output. Hence the high frequency components appear at the output across the resistor. The RL Filter As the inductor is placed in shunt, the DC is allowed to be grounded. The remaining AC component, appears at the output. The symbol for a high pass filter (HPF) is as given below. Frequency Response The frequency response of a practical filter is as shown here under and the frequency response of an ideal HPF when the practical considerations of electronic components are not considered will be as follows. The cut-off frequency for any filter is the critical frequency $f_{c}$ for which the filter is intended to attenuate (cut) the signal. An ideal filter has a perfect cut-off whereas a practical one has few limitations. The RLC Filter After knowing about the RC and RL filters, one may have an idea that it would be good to add these two circuits in order to have a better response. The following figure shows how the RLC circuit looks like. The signal at the input goes through the capacitor which blocks DC and allows AC. Now, that output is again passed through the inductor in shunt, which grounds the remaining DC component if any, present in the signal, allowing AC at the output. Thus we have a pure AC at the output. This is a better high pass circuit than both of them. Band Pass Filter A Filter circuit which allows a set of frequencies that are between two specified values can be termed as a Band pass filter. This filter passes a band of frequencies. As we need to eliminate few of the low and high frequencies, to select a set of specified frequencies, we need to cascade a HPF and a LPF to get a BPF. This can be understood
Electronic Circuits – Power Supplies This chapter provides a fresh start regarding another section of diode circuits. This gives an introduction to the Power supply circuits that we come across in our daily life. Any electronic device consists of a power supply unit which provides the required amount of AC or DC power supply to various sections of that electronic device. Need for Power Supplies There are many small sections present in the electronic devices such as Computer, Television, Cathode ray Oscilloscope etc. but all of those sections doesn’t need 230V AC supply which we get. Instead one or more sections may need a 12v DC while some others may need a 30v DC. In order to provide the required dc voltages, the incoming 230v AC supply has to be converted into pure DC for the usage. The Power supply units serve the same purpose. A practical Power supply unit looks as The following figure. Let us now go through different parts which make a power supply unit. Parts of a Power supply A typical Power supply unit consists of the following. Transformer − An input transformer for the stepping down of the 230v AC power supply. Rectifier − A Rectifier circuit to convert the AC components present in the signal to DC components. Smoothing − A filtering circuit to smoothen the variations present in the rectified output. Regulator − A voltage regulator circuit in order to control the voltage to a desired output level. Load − The load which uses the pure dc output from the regulated output. Block Diagram of a Power Supply Unit The block diagram of a Regulated Power supply unit is as shown below. From the diagram above, it is evident that the transformer is present at the initial stage. Though we had already gone through the concept regarding transformers in BASIC ELECTRONICS tutorial, let us have a glance over it. Transformer A transformer has a primary coil to which input is given and a secondary coil from which the output is collected. Both of these coils are wound on a core material. Usually an insulator forms the Core of the transformer. The following figure shows a practical transformer. From the above figure, it is evident that a few notations are common. They are as follows − $N_{p}$ = Number of turns in the primary winding $N_{s}$ = Number of turns in the secondary winding $I_{p}$ = Current flowing in the primary of the transformer $I_{s}$ = Current flowing in the secondary of the transformer $V_{p}$ = Voltage across the primary of the transformer $V_{s}$ = Voltage across the secondary of the transformer $phi$ = Magnetic flux present around the core of the transformer Transformer in a Circuit The following figure shows how a transformer is represented in a circuit. The primary winding, the secondary winding and the core of the transformer are also represented in the following figure. Hence, when a transformer is connected in a circuit, the input supply is given to the primary coil so that it produces varying magnetic flux with this power supply and that flux is induced into the secondary coil of the transformer, which produces the varying EMF of the varying flux. As the flux should be varying, for the transfer of EMF from primary to secondary, a transformer always works on alternating current AC. Depending upon the number of turns in the secondary winding, a transformer can be classified either as a Step-up or a Step-down transformer. Step-Up Transformer When the secondary winding has more number of turns than the primary winding, then the transformer is said to be a Step-up transformer. Here the induced EMF is greater than the input signal. The figure below shows the symbol of a step-up transformer. Step-Down Transformer When the secondary winding has lesser number of turns than the primary winding, then the transformer is said to be a Step-down transformer. Here the induced EMF is lesser than the input signal. The figure below shows the symbol of a step-down transformer. In our Power supply circuits, we use the Step-down transformer, as we need to lessen the AC power to DC. The output of this Step-down transformer will be less in power and this will be given as the input to the next section, called rectifier. We will discuss about rectifiers in the next chapter. Learning working make money