Abstract: A PWM signal drives a pair of output transistors connected in series between a supply line and ground so that a push-pull current is output toward a speaker via a coil from a point connecting both output transistors. A current limiting resistor has one end connected to the supply line and between the other end and ground is provided a control transistor. Furthermore, a comparator compares the supply line voltage and a reference voltage and turns on the control transistor when the supply line voltage is higher than the reference voltage in the comparison result thereof.

Abstract: The audio reproduction system amplifies and reproduces both a digital audio signal and an analog audio signal. After delta sigma modulation by a ?? modulator, the digital audio signal is pulse width modulated by a first PWM converter and supplied to a selector. The analog audio signal is compared with a PWM carrier signal by a second PWM converter, converted to a PWM signal, and supplied to the selector. A signal selected by the selector is then amplified by a class D amplifier.

Abstract: A PWM signal drives a pair of output transistors connected in series between a supply line and ground so that a push-pull current is output toward a speaker via a coil from a point connecting both output transistors. A current limiting resistor has one end connected to the supply line and between the other end and ground is provided a control transistor. Furthermore, a comparator compares the supply line voltage and a reference voltage and turns on the control transistor when the supply line voltage is higher than the reference voltage in the comparison result thereof.