Therefore, constant output voltages need to be produced across the wide bandwidths of a power amplifier. All the smallsignal amplifiers have been designed so that output voltage can vary in response to both positive and negative inputs. Class a power amplifier is a type of power amplifier where the output transistor is on full time and the output current flows for the entire cycle of the input wave form. Class a power amplifier circuit theory design circuit diagram.
Class a power amplifier is the simplest of all power amplifier configurations. A class a power amplifier is one in which the output current flows for the entire cycle of the ac input supply. Since the transistors in class a amplifier, are forward biased all the time, few current will flow through them even though there is no input signal and this is the main reason for its poor efficiency. To achieve this, the power amplifier must be biased in such a way that no part of the signal is cut off. The circuit diagram of a class a power amplifier is shown in fig.
The limitations due to the efficiency of class a power amplifiers. Classd amplifiers theoretically can reach 100% efficiency, as there is no period during a cycle were the voltage and current waveforms overlap as current is drawn only through the transistor that is on. When the collector current flows at all times during the full cycle of signal, the power amplifier is known as class a power amplifier. We present the first design of a wide bandwidth classs power amplifier for ultrasonic devices. Amplifiers are classified according to their circuit configurations and methods of operation. The output signal varies for a full 360 of the input signal. Explains class a power amplifier load line,output waveform. The principal advantage of the classa amplifier is that it generally produces less signal distortion than some of the other, more efficient classes that we will. As we stated above, a 360degree conduction angle means the amplifier device remains active for the entire time and use complete input signal.
An amplifier that has that property is called a classa amplifier. They have high fidelity and are totally immune to crossover distortion. Part ii to appear later will cover the switching amplifier modes of operation. Amplifier classes and the classification of amplifiers.
In case of class a amplifier, the conduction angle is 360 degree. If the collector current flows all at all times during the full cycle of the signal, the power amplifier is known as class a power amplifier. Tutorial on class a power amplifier circuit with theory,design,circuit diagram. In this paper we present design and implementation of a high efficiency class e, radio frequency rf, power amplifier pa with galliumnitride gan, high electron mobility transistor hemt. Class d amplifier a class d audio amplifier is basically a nonlinear switching amplifier or pwm amplifier. Generally, large signal or power amplifiers are used in the output stages of audio amplifier systems to drive a loudspeaker load. Class a amplifier circuit operation and applications. Class a amplifier is a high gain amplifier with high linearity. When the collector current flows only during the positive half cycle of the input signal.