Abstract: A shock sound prevention circuit which makes a BTL audio amplifier operate stable 100 msec after turning-on of a power supply is offered. The shock sound prevention circuit includes a terminal for reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which the reference voltage is applied as a bias voltage and amplifies the audio signal input from an input terminal, a second operational amplifier to which the reference voltage from the terminal for reference voltage is applied as a bias voltage and amplifies a reverse signal of the audio signal applied to the first operational amplifier, a first and a second buffers to which the reference voltage is applied, a first output terminal to which an output of the first operational amplifier and an output of the first buffer are connected together, and a second output terminal to which an output of the second operational amplifier and an output of the second buffer are connected together.

Abstract: A shock sound prevention circuit which provides a BTL audio amplifier with stable operation about 100 msec after turning-on of a power supply is required. Since the BTL audio amplifier is usually integrated in an IC, use of capacitors which takes up a large pattern area on the IC chip needs to be minimized. This invention offers a shock sound prevention circuit which has a capacitance for reference voltage to generate a reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which an audio signal input and the reference voltage are applied, a second operational amplifier to which a reverse signal of the audio signal input and the reference voltage are applied, a first and a second buffers to which the reference voltage is applied and a level comparator which compares a voltage of the power supply with the reference voltage.

Abstract: A shock sound prevention circuit which makes a BTL audio amplifier operate stable 100 msec after turning-on of a power supply is offered. The shock sound prevention circuit includes a terminal for reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which the reference voltage is applied as a bias voltage and amplifies the audio signal input from an input terminal, a second operational amplifier to which the reference voltage from the terminal for reference voltage is applied as a bias voltage and amplifies a reverse signal of the audio signal applied to the first operational amplifier, a first and a second buffers to which the reference voltage is applied, a first output terminal to which an output of the first operational amplifier and an output of the first buffer are connected together, and a second output terminal to which an output of the second operational amplifier and an output of the second buffer are connected together.

Abstract: A shock sound prevention circuit which provides a BTL audio amplifier with stable operation about 100 msec after turning-on of a power supply is required. Since the BTL audio amplifier is usually integrated in an IC, use of capacitors which takes up a large pattern area on the IC chip needs to be minimized. This invention offers a shock sound prevention circuit which has a capacitance for reference voltage to generate a reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which an audio signal input and the reference voltage are applied, a second operational amplifier to which a reverse signal of the audio signal input and the reference voltage are applied, a first and a second buffers to which the reference voltage is applied and a level comparator which compares a voltage of the power supply with the reference voltage.