Digital amplifier and methods for enhancing resolution and dynamic range of a digital amplifier

An amplifier including a difference amplifier, said difference amplifier including a first output and a second output which are adapted for providing a PWM signal output to a load by signal differencing between said first and said second outputs, said difference amplifier being adapted for operating in at least first and second alternative operating modes which are respectively characterised by first and second operating voltages, wherein pulses of said PWM signal output being substantially symmetrical about the centreline of their respective PWM cycles during said first and second operating modes and being drifted away from said centreline during transition from one operating mode to another so that voltage continuity at said first and said second outputs can be provided during said transition.

An amplifier including control means, signal processing means and a difference amplifier, said difference amplifier including a first output and a second output which are adapted for PWM signal output to a load by signal difference between said first and said second outputs, said difference amplifier being adapted for operating in at least first and second alternative operating modes which are respectively characterised by first and second operating voltages, said control means including means for evaluating the signal characteristics of an incoming signal, means for determining the operating modes of said difference amplifier according to predetermined criteria and means for controlling the operating modes of said difference amplifier, so that, upon detection of a transition signal, said difference amplifier will enter into transition mode before changing its operating modes, wherein, during said transition mode, the pulse area of the pulses of said first and second outputs of said difference amplifier is changed according to a pre-determined manner so that the pulse area of pulses of said first and second outputs at the end of said transitional mode is comparable to that immediately after the change of said operating modes.

An amplifier including a difference amplifier and signal processing means, said difference amplifier including a first output and a second output which are adapted for providing a PWM signal output to a load by signal difference between said first and said second outputs, said difference amplifier being adapted for operating in at least first and second alternative operating modes which are respectively characterised by first and second operating voltages, said signal processing means including means to adjust the output voltages of said first and second outputs, so that, during transition from one operating mode to another, the output voltages of said first and second outputs of said difference amplifier being changed according to a pre-determined manner so that there is a substantial degree of continuity of the output voltages of said first and second outputs and said PWM output during the transition.

A digital amplifier including a higher voltage amplifying branch, a lower voltage amplifying branch, digital signal processing means, control means for selectively amplifying a digital signal alternatively by said higher voltage amplifier branch or said lower voltage amplifying branch for output and for controlling the transition between amplification by said higher voltage amplifier branch and said low voltage amplifier branch, conversion means for converting a digital signal for amplification between said higher voltage amplifying branch and said lower voltage amplifying branch upon detection of a transition signal, wherein, during said transition between amplification by said higher voltage amplifier branch and said lower voltage amplifier branch, the effective pulse area of the digital signal to be amplified by either said higher voltage amplifying branch and said lower voltage amplifying branch remains substantially unchanged.

A digital amplifier comprising a difference amplification means and control means, said difference amplification means comprising means for amplifying first and second pulsed signal streams for producing an amplified signal stream by difference, said difference amplification means operating in first and second alternative operating modes for outputting pulsed signals at first and second voltage levels of unequal amplitudes, said control means gradually changing the pulse widths of signal pulses of said first and second pulsed signal streams during transition between said first and said second operating modes while maintaining a substantially constant difference between the pulse area of the corresponding individual pulses of said first and second pulsed signal streams.