Applications of push pull class b amplifier
The Web This site. In amplifiers using class B bias, illustrated in Fig. This dramatically increases efficiency, compared with class A. The downside for this increased efficiency is that the transistor only amplifies half the waveform, therefore producing severe distortion. However, if the other half of the waveform can be obtained in some other way without too much distortion, then class B amplifiers can be used to drive most types of output device. The aim is to obtain a good power gain with as much of the energy consumed from the power supply going into the load as possible.
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Push-Pull Amplifiers Circuit Diagram, Working and Applications
In earlier days, before the invention of electronic amplifiers , the coupled carbon microphones are used as crude amplifiers in telephone repeaters. The first electronic device that practically amplifies was the Audion vacuum tube, invented by the Lee De Forest in the year The term amplifier and amplification are from Latin word amplificare to expand or enlarge.
The vacuum tube is the only simplifying device for 40 years and dominated electronics up to When the first BJT was in the market it has created another revolution in the electronics and it is a first portable electronic device like transistor radio developed in the year This article discusses the classes and classification of amplifiers.
Simply the amplifiers are called as an amp. The amplifier is an electronic device used to increase the signal of current, voltage and power. The function of the amplifier is by using the power from the power supply and longer altitude, it controls the output signal with the help of input signal.
An amplifier modulates the out of the power supply is based on the properties of the input signal. The amplifier is quite opposite to an attenuator if the amplifier provides the gain, hence the attenuator provides the loss. The amplifier is also a discrete part of the electrical circuit which is continued with the other device. An amplifier is used in all the electronic equipments. The amplifiers can be categorized in different types.
The first one is by the frequency of the electronic signal being improved. The next one is the audio amplifier and amplifies the signal in the range of less than the 20 kHz and the RF amplifier amplifies the radio frequency ranges from 20 kHz to KHz. The last one is current quality and voltage are being amplified. There are different types of amplifiers includes a current amplifier, a voltage amplifier or the transconductance amplifier and trans-resistance amplifier.
Nowadays, most of the amplifiers used in the market are transistors but, vacuum tubes are also using in some of the applications. The classification of amplifiers is shown in the following. The electronic amplifier uses only one variable i. It may be current or voltage can be used in the input or either in the output.
There are four types of amplifiers and which are dependent on the source used as a linear analysis. The classification of the amplifier is based on the device terminal which is common to both input and output circuit. In the Bipolar Junction Transistor, there are three classes namely.
In the case of Field Effect Transistor , it has the corresponding configurations like common source, common gate, and a common drain. The common emitter is the most frequently to provide amplification of a voltage applied between base and emitter. The input signal is in between collector and emitter is inverted it is relative to the input. The common collector circuit is called as an emitter follower, source follower, and cathode follower.
The amplifier whose output displays no feedback to the input side is called as unilateral. The unilateral amplifier of the input impedance is independent of load and the output impedance is independent signal source impedance. The amplifier which uses the feedback to connect part of the output back to the input is called as a bilateral amplifier.
The input impedance of bilateral amplifier depends on the load and the output impedance of source impedance. The linear unilateral and bilateral amplifiers are denoted as two port networks. In this, the classification of an amplifier uses the phase relationship of the input signal to the output signal. The inverting amplifier gives the output of degrees out of phase with the input signal.
The non-inverting amplifier continuous the phase of the input signal waveforms and the emitter is a non-inverting amplifier. The voltage follower is called as non-inverting amplifier and it has unity gain. This type of amplifier is classified by using the coupling method of the signal at the input, output and between the stages. There are different types of methods in the interstage coupling amplifier. There are different types of classes of amplifiers mentioned in the following.
The class A amplifiers are simple designed amplifiers and this amplifier is mostly commonly used amplifiers. Basically, the class A amplifiers are the best class amplifiers because of their low distortion levels. This amplifier is the best in the audio sound system and in most of the sound system use the class A amplifier. The class A amplifiers are formed by the output stage devices which are biased for the class A operation.
By comparing the other classes amplifiers to class A amplifier has the highest linearity. To obtain high linearity and gain in class A amplifier the output of the class A amplifier should be biased ON for all times. Hence the amplifier is said to be as a class A amplifier. The zero signal ideal current in the output stage should be equal to or more than the maximum load current is required to produce more amount of signal.
The class B amplifiers are the positive and negative halves of the signals, that are allocated to the different parts of the circuits and the output device switched ON and OFF continuously. The basic class B amplifiers are used in two complementary transistors which are FET and bipolar.
These two transistors of each half of the waveform with its output are configured in a push-pull type arrangement. Hence the each amplifier only half of the output waveform.
In the Class B amplifier, if the input signal is positive, then the positively biased transistor conduct and the negative transistor is switched OFF. If the input signal is negative, then the positive transistor switches OFF and negative biased transistor turn ON. Hence the transistor conduct half of the time whatever it may be like positive or negative half cycle of the input signal. The class AB is the combination of class A and class B amplifier.
The class AB amplifiers are using commonly in the audio power amplifiers. Then the device may be FET or bipolar will be ON for more than the one-half of the cycle, but it is less than the one full cycle of the input signal.
Hence, in the class AB amplifier design each of the push-pull transistors is conducting slightly more than the half cycle of conduction in class B, but much less than the full cycle of conduction of class A. The conduction angle of Class AB amplifier is in between to which is depending on the bias point.
The advantage of the small bias voltage is to give in series resistance and diode. The design of class C amplifier has a great efficiency and poor linearity.
In the previous amplifiers, we have discussed the class A, B and AB are the linear amplifiers. The class C amplifier is a deeply biased hence the output current is zero for more than the one-half of the input signal and the transistor idling at the cut off point. Because of the serious audio distortion, the class C amplifiers are high-frequency sine wave oscillation. The class D amplifier is non-linear switching amplifiers or PWM amplifiers.
The voltage and the current waveforms overlap current is drawn only with the help of transistor which is in ON state. These amplifiers are also called as the digital amplifiers. The design of the class D amplifier is more complex than the class AB amplifier.
The F amplifiers are used to increase the efficiency and output by the harmonic resonators in the form of output network and to shape the output waveform in a square wave.
The class S amplifiers are similar operations to the class D amplifiers. These amplifiers are Non-linear switching mode amplifiers. It converts the analog input signals to the digital square wave pulses by using the delta-sigma modulations. It amplifies them in to increase the output power by the help of band pass filter. The class T amplifiers are designed with a type of digital switching amplifiers.
Nowadays these amplifiers became more popular as an audio amplifier design because of the extension of the DSP chip and multi-channel sound amplifier. This amplifier converts the signal from analog signal to the digital pulse width modulation signal and the amplification increase the efficiency of an amplifiers.
The class T amplifiers are the combination of low distortion signal of class AB amplifier and the other one is the efficiency of class D amplifier.
The class G amplifier used in the multiple power supply rails of different voltages. Automatically switches between the supply rails as the input signal changes. The contact switching decreases the average power consumption hence, the power loss is produced by the wasted heat. The below circuit diagram shows the class G amplifier. This article describes the classification of amplifiers. Furthermore any queries, felt anything missed, you want to know any info about any particular topic, please let me know by commenting in the comment section below.
Here is a question for you, What are the functions of different types of amplifiers? Found it missing. If possible can you tell where can I get it? Any URL. Share This Post: Facebook.
CLASS B and Class AB Push Pull Amplifier
Push-Pull Amplifier is a power amplifier which is used to supply high power to the load. One transistor pushes the output on positive half cycle and other pulls on negative half cycle, this is why it is known as Push-Pull Amplifier. The advantage of Push-Pull amplifier is that there is no power dissipated in output transistor when signal is not present. Class A configuration is the most common power amplifier configuration. It consists of only one switching transistor which is set to remain ON always. It produces minimum distortion and maximum amplitude of output signal. The stages of the Class A amplifier allows same amount of load current to flow through it even when there is not input signal connected, therefore large heatsinks are needed for the output transistors.
Push–pull output
A push—pull amplifier is a type of electronic circuit that uses a pair of active devices that alternately supply current to, or absorb current from, a connected load. This kind of amplifier can enhance both the load capacity and switching speed. Push—pull outputs are present in TTL and CMOS digital logic circuits and in some types of amplifiers , and are usually realized by a complementary pair of transistors , one dissipating or sinking current from the load to ground or a negative power supply, and the other supplying or sourcing current to the load from a positive power supply. A push—pull amplifier is more efficient than a single-ended "class-A" amplifier. The output power that can be achieved is higher than the continuous dissipation rating of either transistor or tube used alone and increases the power available for a given supply voltage. Symmetrical construction of the two sides of the amplifier means that even-order harmonics are cancelled, which can reduce distortion. However, the push—pull amplifier requires a phase-splitting component that adds complexity and cost to the system; use of center-tapped transformers for input and output is a common technique but adds weight and restricts performance. If the two parts of the amplifier do not have identical characteristics, distortion can be introduced as the two halves of the input waveform are amplified unequally. Crossover distortion can be created near the zero point of each cycle as one device is cut off and the other device enters its active region. Push—pull circuits are widely used in many amplifier output stages.
Class-B Pushpull Amplifier Operation
In this new tutorial, we will present in detail another class of amplifiers known as Class B that have been developed as an answer to the low efficiency of the Class A. In the first section, we will present what a Class B amplification consists of and an overview of its characteristics. We will see in a later section, however, that in order to work properly, two complementary transistors are needed in order to ensure the reproduction of the input signal, in what is commonly known as a push-pull configuration. Moreover, we will highlight an undesired distortion happening in Class B amplifiers and some possible solutions to limit it. At the last section of this tutorial, we will give a step by step method on how to calculate the theoretical maximum efficiency of Class B amplifiers.
Lecture # 16 &17 Complementary symmetry & push-pull Amplifiers
The world has always enjoyed listening to high quality audio, whether in our homes or in our vehicles. Over the years many amplifier configurations have been used to deliver a faithful signal at high power levels, with improved efficiency. The path of amplifier evolution has incorporated both the analog and the digital domains, spawning a variety of topologies including Class AB and Class D, which remain in common use. As with many sectors that are based on well-defined topologies, each can be shown to have its own strengths and weaknesses, while still remaining a valid choice for a particular application type. For example, push-pull Class B amplifiers were designed to be more efficient than the foregoing Class A topology, but Class B suffered with linearity issues due to the way that they switched. This was then addressed in the later Class AB topology, which switched in the linear region of the transistor.
Push-Pull Amplifier Circuit – Class A, B & AB Amplifier Circuits
Continue with email. The fig a shows class B output stage that consists of a complementary pair of bipolar transistor. E junction of Qp is baised. If vi becomes negative by more than 0. Transistor QP is a sink for the load current, which means it is negative. When either of the transistor is conducting, the voltage gain is unity as a result of emitter followers.
The relation between the maximum power output and the maximum power dissipation in each transformer is given by. For an ideal class B push-pull amplifier, the maximum output power is five times the maximum power dissipation in each transistor. Start Learning English Hindi. This question was previously asked in.
A push pull amplifier is an amplifier which has an output stage that can drive a current in either direction through through the load. The output stage of a typical push pull amplifier consists of of two identical BJTs or MOSFETs one sourcing current through the load while the other one sinking the current from the load. Push pull amplifiers are superior over single ended amplifiers using a single transistor at the output for driving the load in terms of distortion and performance. A single ended amplifier, how well it may be designed will surely introduce some distortion due to the non linearity of its dynamic transfer characteristics.
The Application Activity in this is a public address system. Recall that the complete system includes the preamplifier, a power amplifier, and a dc power supply. You will focus on the power amplifier in this section and complete the total system by combining the three component parts. Power amplifiers are large-signal amplifiers. This generally means that a much larger portion of the load line is used during signal operation than in a small-signal amplifier. In this section, we will cover four classes of power amplifiers: class A, class B, class AB, and class C. These amplifier classifications are based on the percentage of the input cycle for which the amplifier operates in its linear region.
Facebook Twitter. Class-B Pushpull Amplifier Operation: Class - B operation is provided when the dc bias leaves the transistor biased just off, the transistor turning on when the ac signal is applied. This is essentially no bias, and the transistor conducts current for only one-half of the signal cycle. To obtain output for the full cycle of signal, it is necessary to use two transistors and have each conduct on opposite half-cycles, the combined operation providing a full cycle of output signal.
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