Stabilized rail-to-rail speaker driver circuit

Abstract

A rail-to-rail driver amplifier circuit that utilizes complementary output transistors to fully utilize the available power supply voltage. The circuit includes an input pre-amplifying circuit for receiving the audio signal and for receiving electrical energy from a power supply having a first rail at a positive potential and a second rail at a negative potential to produce a pre-amplified output signal. The circuit further includes a first output driver circuit having a voltage gain limited current amplifier coupled to the first rail and to a first output terminal of the input pre-amplifying circuit and a second output driver circuit having a voltage gain limited current amplifier coupled to the second rail and to a second output terminal of the input pre-amplifying circuit. The input pre-amplifying circuit is operable to supply the pre-amplified output signal to one of the output driver circuits when the input signal current exceeds a current threshold and to the other of the output driver circuits when the input signal current is below the current threshold. The complementary speaker driver output circuits are mirrored about the voltage appearing at a capacipacitance. This voltage will equal the value of the system signal ground which is usually midway between the positive and negative power supply rails (Vmid).