Class-A and A / B amplifier
work still today, most audio systems in Class-A/B- or A mode. This traditional amplifier technology is extremely inefficient, since a large amount of energy is lost as a pure loss of heat. The real energy wasters are the amplifiers in the A-operation, because the theoretical maximum efficiency is 25%. The amplifiers used in most A / B operation - with a theoretical maximum efficiency of 78.5% - see because at first glance a lot better off. In listening conditions in practice, at 30% full load, then arises, however, only one, an efficiency around 35%. Of course, such amplifiers also require correspondingly large-sized power supplies.
With all these drawbacks, the advantage of this amplifier group, however, that relatively simple superior sound data can be realized.
Class-D amplifier
A good efficiency have "digital" amplifier. These amplifiers are clocked as many switching power supplies with pulse width modulation. Even under typical listening conditions, the efficiency of a Class D amplifier still between 65% and 80%. The good efficiency needs to be paid for with relatively poor sound data and a high THD (distortion). Furthermore, the pulse width modulation in amplifiers at EMC aspects (electromagnetic compatibility) is extremely problematic and difficult to get a grip.
The philosophy of the clocked amplifier based on the fact that the power semiconductors of the power amplifier connected through either completely or locked. Only in the shortest possible period during the switching process (transition from "high" after "Low" or vice versa), the semiconductor is in linear operation. The steeper the switching edges, the lower the power loss.
Although the circuit of a Class D amplifier is not necessarily complicated, the conductor track routing in the layout, and especially the ground wiring, be done with utmost care. Interference between switching transients and low-level signals are otherwise inevitably occur. These disorders affect significantly the sound quality of the amplifier.
Class-T Amplifier
A new amplifier technology is now the high-tech company Tripath in the USA. Unlike Class-D amplifiers have Class-T amplifiers that use the so-called Digital Power Processing (DPPTM) technology is very low intermodulation distortion.
Class-T amplifiers work on an adaptive spread spectrum technology with sampling frequency of 200 kHz and 1.5 MHz. The highly integrated amplifier modules consist of all digital and analog components that are needed to build the amplifier. In essence, a signal processor is integrated with the help of adaptive algorithms, the characteristics of the FET transistors learn about the exact timing to be able to control them. In principle, however, be said that is relatively easy due to the high degree of integration with the Tripath amplifier modules, the development of a digital amplifier. As with the Class-D amplifiers here for good technical data layout, and in particular the grounding of decisive importance. rest
output filter
Since the direct amplifier outputs high-frequency wave signals are essential for the reconstruction of the audio data output filter is required.
Purpose for Class-T
The possibilities of the new amplifier technology are manifold. In addition to high power amplifiers will certainly keep the Class-T technology in many consumer products collection. Especially if space is available, or the dissipation of heat loss is difficult. Further developments are so-called "True Digital Amplifier," in which a digital signal is first converted, shortly before the speaker terminals into an analog audio signal. Corresponding blocks of Tripath amplifiers are about to launch. Only then can we really speak of a digital amplifier.
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