Abstract: An input stage for an audio power amplifier is provided. The input stage includes a fully differential amplifier and a supply-independent reference voltage generator. The supply-independent reference voltage generator provides a supply-independent reference voltage that is used as the common mode voltage of the output of the fully differential amplifier.

Abstract: A fully differential class D amplifier is provided. The class D amplifier includes an active amplifier in the feedback path of the modulator. In one embodiment, the class D amplifier includes a fully differential amplifier as an input buffer, in which a supply-independent reference voltage is used as the common mode voltage of the output of the fully differential amplifier. In one embodiment, the class D amplifier includes a pulse width modulation circuit that includes rail-to-rail comparators.

Abstract: An amplifier circuit with improved turn-on transient operation includes a differential amplifier and a selectively variable reference generator for controlling the amplifier output during circuit turn-on. The amplifier is biased by a single power supply and its differential inputs are driven by a first reference voltage from the reference generator and a single-ended input signal. Following circuit turn-on and turn-off, the first reference voltage typically charges to or discharges from, respectively, some fixed value relative to the positive power supply voltage. A comparator detects when the first reference voltage exceeds a second reference voltage and generates a control signal in response to that transition. The second reference voltage is selected to be nearly the steady-state value of the first reference voltage. The control signal (which indicates that the first reference voltage is nearing its steady-state value) is fed to a delay circuit which generates a delayed control signal.