Shenzhen Sts Microelectronics Co., Ltd.

Wen Li Luo

Solomon Ng

An audio amplifier device includes a power supply having an output for providing a supply voltage, a voltage divider connected to the output of the power supply for providing a divided supply voltage, and an audio amplifier that further includes a supply voltage rejection circuit. The audio amplifier has a first input for receiving an input audio signal, a second input for receiving the supply voltage, a third input for receiving a supply voltage rejection signal for the supply voltage rejection circuit, and an output for providing an output audio signal. A power-off noise suppression circuit has a first input for receiving the divided supply voltage and an output for providing the supply voltage rejection signal. The power-off noise suppression circuit sets the supply voltage rejection signal equal to the divided supply voltage during power-off of the power supply so that a rate of decrease of the supply voltage is greater than a rate of decrease of the supply voltage rejection signal for reducing noise in the output audio signal during the power-off.

Power-off noise suppression circuit and associated methods for an audio amplifier device

A voltage regulator includes a power transistor receiving a drive current, and a current limit protection circuit connected to the power transistor. The current limit protection circuit includes a first resistance connected to the power transistor for sensing an output current, a limit switch transistor connected to the power transistor and to the first resistance, and a current generator and second resistance connected thereto. The current generator and second resistance biases the limit switch transistor to divert drive current from the power transistor based upon the output current through the first resistance exceeding a threshold. The first resistance has a value less than a value of the second resistance. The first resistance can be made considerably smaller than otherwise to thereby reduce power consumption. The temperature coefficient for the second resistance is balanced with respect to a temperature coefficient for the first resistance so that a output current from the voltage regulator is not sensitive to temperature variations.

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