So how did they do it? The solution is actually fairly simple in concept: where Class B utilizes a push/pull arrangement with each half of the output stage conducting for 180 degrees, Class A/B amplifiers bump that up to ~181-200 degrees. Thanks to this combination of strengths, Class A/B amplifiers largely dominate the consumer market. Class A/BĬlass A/B, as one might deduce, combines the best of Class A and Class B in order to create an amplifier without the drawbacks of either. Needless to say, such distortion in sufficient amounts is audible, and while some Class B designs were better than others in this respect, Class B didn’t receive much love from audiophiles. The reason for this is known as crossover distortion.Ĭrossover distortion affecting a simple sine wave image courtesy of .Īs seen in the image above, crossover distortion is a problem/delay in the handoff between the devices handling the positive and negative portions of the waveform. In spite of their obvious strength, the odds are good you won’t see too many pure Class B amplifiers floating around.
#Class a power amplifier professional
Given the relatively high efficiency, Class B was used in some professional sound reinforcement amplifiers as well as some home audio tube amps. As a consequence, Class B amplifiers are substantially more efficient than their Class A counterparts, with a theoretical maximum of 78.5%.
![class a power amplifier class a power amplifier](https://media.cheggcdn.com/media%2Fa4d%2Fa4d34620-1b18-418f-ad04-551e2b12a545%2FphpNahsVo.png)
While all of the output devices in a Class A amplifier are conducting 100% of the time, Class B amplifiers utilize a push/pull arrangement in such a way that only half the output devices are conducting at any given time: one half covers the +180 degree portion of the waveform, while the other covers the -180 degree section. Real world efficiency rates can be on the order of 15-35%, with the potential to drop into the single digits using highly dynamic source material. This is further exacerbated by the fact that Class A designs require relatively high levels of quiescent current, which is the amount of current flowing through the output devices when the amplifier is producing zero output. The requirement of Class A designs to have all output devices conducting at all times results in significant amounts of wasted power, which is ultimately converted to heat. However, there is one important drawback to these designs: efficiency.
![class a power amplifier class a power amplifier](https://ae01.alicdn.com/kf/HTB19dYfXBUSMeJjy1zdq6yR3FXa4.jpg)
In addition, push/pull Class A designs are less susceptible to hum single ended designs tend to require special attention to the power supply to mitigate this issue.Ī simple Class A diagram (left courtesy of ) and a high powered Class A amplifier, the Pass Labs XS150 (right).īecause of the positive attributes associated with Class A operation, it is considered the gold standard for audio quality in many audiophile circles.
#Class a power amplifier full
While both devices are conducting through the full 360 degree cycle, one device will shoulder more of the load during the positive portion of the cycle, while the other handles more of the negative cycle the primary advantage of this arrangement is reduced distortion relative to single ended designs, as even order harmonics are cancelled out. Push/pull diverges from the basic explanation above by utilizing output devices in pairs. Class A can also be broken down into single ended and push/pull amplifiers.
![class a power amplifier class a power amplifier](https://electronicscoach.com/wp-content/uploads/2018/05/class-a-circuit-diagram.jpg)
The defining principle of Class A operation is that all of an amplifier’s output devices must be conducting through the full 360 degree cycle of a waveform. Sinewave - a full wavelength represents 360 degrees Class AĪs compared with the other amplifier classes we’ll cover, Class A amps are relatively simple devices. We are going to be discussing how amplifiers conduct through waveforms, so a basic diagram of a sinewave is shown below. So what does our alphabet soup of amplifier classes mean? Keep reading to find out but first watch our recently added YouTube video discussion! While each amplifier class comes with its own set of strengths and weaknesses, their job (and how end performance is judged) remains the same: to amplify the waveform sent to it by a preamplifier without introducing distortion, or at least as little as possible distortion. These classes aren’t simple grading systems, but descriptions of the amplifier’s topology, i.e.
![class a power amplifier class a power amplifier](http://1.bp.blogspot.com/-1z4cqsL4vcE/WQEUbAsth9I/AAAAAAACD0I/OOIsPPer5VQOK09Ywo-7dBDKPQ7TkZz_wCK4B/s1600/ClaseA_detalle-aluminio2.jpg)
Typically denoted by a letter or two, the most common amplifier classes used in consumer home audio today are Class A, A/B, D, G, and H. If you’ve ever glanced at the specifications sheet for an amplifier, one of the things you may have noticed is the amplifier’s class.