Power amplifier providing high efficiency

A device comprising:

• a battery, a speaker, a processing block and an integrated circuit (IC), wherein said IC comprises:
• a DC-DC converter coupled to receive power from said battery and to generate a regulated power supply voltage as output, wherein a magnitude of said regulated power supply voltage is controlled by the magnitude of a control signal provided to said DC-DC converter;
• a first linear amplifier coupled to receive a first input signal from said processing block, said first input signal varying in amplitude continuously in each of a sequence of time intervals, said first linear amplifier designed to amplify said first input signal to generate a power-amplified output signal, said power-amplified output signal also varying in amplitude continuously in each of said sequence of time intervals, wherein said first linear amplifier is coupled to receive said regulated power supply voltage for operation, wherein said power-amplified output signal is coupled to drive said speaker;
• and
• a control block coupled to receive said first input signal, and to generate said control signal with a magnitude having positive correlation with instantaneous amplitude of said first input signal,
• wherein the operation of said control block in conjunction with said DC-DC converter causes said regulated power supply voltage to continuously track instantaneous values of amplitude of said power-amplified output signal in each of said sequence of time intervals such that a difference of instantaneous amplitude of said regulated power supply and said power-amplified output signal is sought to be maintained constant throughout all of said sequence of time intervals,
• wherein said regulated power supply voltage continuously tracks said amplitude of said power-amplified output signal when the amplitude of said power-amplified output signal is in a first range less than the voltage output by said battery, as well as when the amplitude of said power-amplified output signal is in a second range greater than or equal to the voltage output by said battery.