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Literature Review on "Power Amplifier"

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Literature Review on "Power Amplifier"
Answered Same Day Aug 16, 2021 Macquaire University


Ivsn answered on Aug 16 2021
115 Votes
Introduction to Power amplifier:
Most extensively used component in Electronic circuits is amplifiers which tend to increase the signal power. By consuming energy from power supply, they match the output signal with that of input signal waveform but with higher amplitude. Hence, in this manner amplifier changes the quality of output signal to make it stronger than input signal. “Voltage” amplifier generally come under the category of small signal amplifier as they change the small voltage input signal to high output voltage signal. Occasionally, amplifier circuit can also be used to drive a motor circuit or feed a high magnitude signal. And for such type of applications, power amplifiers are needed to maintain high magnitude switching cu
ents [1].
Working of Power Amplifier:
Power amplifier, also called as large signal amplifier delivers required power to the load having magnitude of output signal power higher than that of input signal power. Mainly these types of amplifier circuits are employed in audio amplifier in order to feed loudspeakers. Voltage amplifier and Power amplifier classification is performed basing upon the input and output signal characteristics and the time taken by input to allow cu
ent to flow in the output network. Power amplifier circuit is similar to a DC - DC converter or RF oscillator, which changes DC power signal to constant wave signal [2]. But, ideal power amplifier changes DC power into output signal with the linear control of Radio Frequency input. Hence, wireless PA can also be called as DC-to-modulated- RF converter.
Figure 1 Generalized model of Power Amplifie
Above figure 1 represents the general model of power amplifier in which is the supply voltage, is the load resistance and with RF choke. Inductor present in the circuit has a large value to allow sufficient constant cu
ent through drain of amplifier. Here, transistor is considered as NMOS apart from which any type of transistor can be employed in PA applications.
Classification of power amplifier basing on output voltage and cu
ent wave forms:
The most common type of classification of PA is based upon the voltage and cu
ent waveforms. Each type of PA tends to have its own linearity, output power, power gain and overall efficiency. The different types of power amplifiers are
iefly described below,
Class A Power Amplifier - During the full cycle of output signal, the collector cu
ent flows through the circuit at all times then it is called as class A Amplifier. Therefore, device will conduct even when there is no cu
ent flowing in the circuit which is the main reason for less efficiency of this class power amplifier.
Class B Power Amplifier - In this class of Amplifiers, device will be biased at threshold voltage only. Therefore, conduction angle reduces to , rather than as that in class A Amplifier [3]. Apart from the linearity, the efficiency of this class of amplifiers is high compared with previous class.
Class AB Power Amplifier - This class of amplifiers maintains a balance between linearity and efficiency. And the conduction angle lies between and with the increase in the conduction angle, efficiency reduces but linearity gets improved. A 3 GHz integrated class AB power amplifier developed for WLAN and Mobile WiMAX applications is designed in [4]. In this application, a saturated power of 27.9 dBm and PAE of 12.7% is achieved.
Class C Power Amplifier - In this type of PA, conduction angle will be less than Linearity is lower than class B but efficiency can be made to 100% by substituting conduction angle value near to zero.
Further they can be classified into class D,...

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