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Electronic Circuits
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
Figure 4-36(b) shows the input-output waveforms of a class B amplifier. The operating point of this amplifier is adjusted near the cutoff point. With a sine wave applied to the input, only one alternation of the signal is reproduced. When using class B amplifiers it is possible to get a large change in output for one alternation. Two class B amplifiers working together can each amplify one alternation of a sine wave. When the wave is restored, a complete sine wave is developed. Class B amplifiers are commonly used in push-pull audio output circuits. These amplifiers are usually concerned with power amplification. A class AB amplifier has its operating point between class A and class B. It reproduces all of one input alternation and only part of the other alternation at its output.
Radio Frequency Amplifier Basics
Published in Abdullah Eroglu, Introduction to RF Power Amplifier Design and Simulation, 2018
In class B mode of operation, amplifier efficiency is sacrificed for linearity. When it is desirable to have an amplifier with better efficiency than the class A amplifier, and yet better linearity than the class B amplifier, then class AB is chosen as a compromise. The conduction angle for the class AB amplifier is between 180° and 360°. As a result, the bias point for class AB amplifiers is chosen between the bias points for class A and class B amplifiers. Class AB amplifiers are widely used in RF applications when linearity and efficiency together become requirements. The ideal efficiency of class AB amplifiers is between 50% and 78.53%. The typical drain-to-source voltage and drain current waveforms are illustrated in Figure 1.33.
High-Efficiency Power Amplifiers
Published in Choi Jung Han, Iniewski Krzysztof, High-Speed and Lower Power Technologies, 2018
Guillermo Velasco-Quesada, Herminio Martínez‑García, Alfonso Conesa-Roca
When technological limitations did not allow high-quality PNP power transistors, a balanced center-tapped input transformer, which splits the incoming waveform signal into two equal halves and which are 180o out of phase with each other, could be used in order to obtain a class-B power amplifier. Another center-tapped transformer on the output is used to recombine the two signals, providing the increased power to the load. The transistors used for this type of transformer push-pull amplifier circuit are both NPN transistors with their emitter terminals connected together. Obviously, two of the main disadvantages of this kind of class-B power amplifier are that it uses balanced center-tapped transformers in its design, making it expensive and difficult to construct, and an increase of stage losses.
Realisation of low voltage low power class AB OTA and its application in biquadratic filter
Published in International Journal of Electronics Letters, 2023
Class AB amplifier boosts the current both at the differential input transistors and at the active load. This double improving permits very wide dynamic range currents and concurrently a high current efficiency because the large dynamic current is produced in the output branch without internal replication.