Life expectancy at birth – an estimate of the expected life span of an average newborn child – has been rising around the world. According to the United Nations, global life expectancy at birth increased from 48 years in the 1950 to 1955 period to 69 years in 2010-2015, and it is expected to continue to rise over the next four decades. 24 People in many (though not all) countries are living longer due to increased access to healthcare, improvements in diet and hygiene, effective responses to infectious disease, and many other factors.
The major advantage of a class-D amplifier is that it can be more efficient than an analog amplifier, with less power dissipated as heat in the active devices. Given that large heat sinks are not required, Class-D amplifiers are much lighter weight than analog amplifiers, an important consideration with portable sound reinforcement system equipment and bass amplifiers . Output stages such as those used in pulse generators are examples of class-D amplifiers. However, the term mostly applies to power amplifiers intended to reproduce audio signals with a bandwidth well below the switching frequency.