Abstract: An audio device includes a jack, a switch, an amplifier, an internal sound producer, and a determining circuit. The jack establishes a connection with an external sound producer. The switch is in an opened state when the connection is established, and in a closed state when the connection is open. The amplifier amplifies audio signals to amplified audio signals and sends the amplified audio signals to the switch. The determining circuit receives the amplified audio signals from the switch, and generates a high voltage to control the amplifier not to output the amplified audio signals to the internal sound producer when the switch is in the closed state, and generates a low voltage to control the amplifier to output the amplified audio signals to the internal sound producer. The determined circuit further filters out the amplified audio signals when the switch is in the opened state.

Abstract: An audio apparatus includes an input, a first resistor, a first capacitor, an amplifier, a second resistor, a second capacitor, and an output. The input is used for inputting audio signals. The first resistor and the amplifier are serially connected to the input; wherein the first resistor is connected to the inverting input of the amplifier and the non-inverting input of the amplifier is connected to ground. The first capacitor has one end connected to a node between the first resistor and the inverting input of the amplifier, the other end connected to ground. The second resistor has one end connected to a node between the first resistor and the inverting input of the amplifier, the other end connected to the output of the amplifier. The second capacitor is connected between the inverting input and the output of the amplifier. The output is connected to the output of the amplifier, for outputting the audio signals after processing.

Abstract: An audio amplifier is provided. The audio amplifier includes an amplifier, a biasing circuit, and a time-delay circuit. The amplifier circuit is for amplifying audio signals. The biasing circuit is for providing a bias voltage to the amplifier circuit to actuate the amplifier circuit. The time-delay circuit is for receiving a pulse signal and delaying the bias voltage to avoid a sudden actuation of the amplifier circuit based on the pulse signal. The time-delay circuit comprises a first input for receiving the pulse signal, a first resistor coupled to the first input, a first output coupled to the biasing circuit, a first BJT whose base, emitter, collector are respectively coupled to the first resistor, ground, and the first output.

Abstract: An audio device includes a jack, a switch, an amplifier, an internal sound producer, and a determining circuit. The jack establishes a connection with an external sound producer. The switch is in an opened state when the connection is established, and in a closed state when the connection is open. The amplifier amplifies audio signals to amplified audio signals and sends the amplified audio signals to the switch. The determining circuit receives the amplified audio signals from the switch, and generates a high voltage to control the amplifier not to output the amplified audio signals to the internal sound producer when the switch is in the closed state, and generates a low voltage to control the amplifier to output the amplified audio signals to the internal sound producer. The determined circuit further filters out the amplified audio signals when the switch is in the opened state.

Abstract: An audio apparatus includes an input, a first resistor, a first capacitor, an amplifier, a second resistor, a second capacitor, and an output. The input is used for inputting audio signals. The first resistor and the amplifier are serially connected to the input; wherein the first resistor is connected to the inverting input of the amplifier and the non-inverting input of the amplifier is connected to ground. The first capacitor has one end connected to a node between the first resistor and the inverting input of the amplifier, the other end connected to ground. The second resistor has one end connected to a node between the first resistor and the inverting input of the amplifier, the other end connected to the output of the amplifier. The second capacitor is connected between the inverting input and the output of the amplifier. The output is connected to the output of the amplifier, for outputting the audio signals after processing.

Abstract: An audio amplifier is provided. The audio amplifier includes an amplifier, a biasing circuit, and a time-delay circuit. The amplifier circuit is for amplifying audio signals. The biasing circuit is for providing a bias voltage to the amplifier circuit to actuate the amplifier circuit. The time-delay circuit is for receiving a pulse signal and delaying the bias voltage to avoid a sudden actuation of the amplifier circuit.