Patent ID: 7932711

Claim:
An apparatus comprising: a power supply; an amplifier that is coupled to the power supply and that receives an input signal and generates an output signal; a controller that generates a first control signal and a second control signal, wherein the controller provides the first control signal to the power supply so as to activate and deactivate the power supply; a voltage setting circuit that is coupled to the controller so to receive the second control signal, wherein the voltage setting circuit generates a digital signal based at least in part on the second control signal that corresponds to a magnitude of a reference voltage, and wherein the controller varies the second control signal at power-up such that the magnitude of the reference voltage is increased from a reference potential to a predetermined potential at a predetermined rate, and wherein the controller varies the second control signal at power-down such that the magnitude of the reference voltage is decreased from the predetermined potential to the reference potential at the predetermined rate; and a voltage generator having: a digital-to-analog-converter (DAC) that is coupled to voltage setting circuit so as to receive the digital signal; and a filter that is coupled between the DAC and the amplifier so as to provide the reference voltage to the amplifier; wherein the controller further comprises a first controller, and wherein the voltage setting circuit further comprises: a second controller that is coupled to the first controller and the DAC; and a memory that is coupled to the controller; wherein the DAC further comprises: a subtracter that is coupled to the second controller; an adder that is coupled to the subtracter; a first delay circuit that is coupled to the adder; a quantizer that is coupled to the adder and the filter; a second delay circuit that is coupled to the quantizer; and a coefficient setting circuit that is coupled to the second delay circuit and the subtracter.