Class A amplifiers are the simplest form of a power amp. The reason is that, to produce an inverted output, they use a single switching transistor in its standard configuration. Since the transistor is always on, it is able to conduct during the complete cycle of the input signal waveform.
The Class A amplifier configuration is the ideal operating model because it is capable of generating minimum distortion. In addition, it offers the maximum amplitude of the output signal. It’s so efficient that it’s impossible to have a crossover or a switch-off distortion to the output waveform in any part of the cycle. In contrast to other amps, Class A ones use a single power transistor or a joined one to share high load current.
Class A Amplifiers: Characteristics
Class A amps use the whole input signal. The active element conducts for the full process. A key characteristic (in fact, the best-known) is that the output stage devices are biased for any Class A operation. When there is a higher signal distortion, the subclass A2 might refer to vacuum-tube Class A stages. These stages drive the grid to the positive side of the signal peak in order to use more power than the usual.
Class A amplifiers tend to have a rather simple design compared to the designs of the Class B and Class AB amps. The former use a single-ended unit. On the one hand, the amplifying component is biased so the unit is always conducting, whereas the inactive current is very close to the most linear portion of its transconductance curve. On the other, Class B and Class AB amplifiers need to have two connected devices in the circuit. Each of them is in charge of half of the waveform.
Final Thoughts on Class A Amps
Class A amplifiers are never really off, so they don’t have any problems with charge storage. They have a great high-frequency performance, a rather stable feedback loop, and fewer high-order harmonics. Because there is no zero signal, there is no conflict with crossover distortion. This characteristic is great for low signal levels of radio receivers because of its fairly low levels of distortion.
