Abstract: A class D audio amplifier provides both an audio output signal and a DC bias voltage to an electrostatic transducer (9). In the amplifier, a modulated sequence of pulses is generated by an input module (1) in response to an input audio signal. The sequence of pulses is amplified by an output module (3) using high speed switching output transistors (4, 5). An output signal is generated by applying a low pass filter (8) to the amplified pulses, and the output signal is provided to the transducer to produce audible output. The amplified sequence of pulses is also used to drive a voltage multiplier module (10) to provide bias voltage for the electrostatic transducer (9). In other embodiments, the bias voltage is provided by a bias voltage module which reverses the bias voltage at intervals, and a phase reverser (13) reverses the phase of the signals fed to the output module (3) simultaneously with reversal of the bias voltage.

Abstract: An electrostatic transducer comprises an electrically conductive first layer (1), a flexible insulating second layer (25) disposed over the first layer, and a flexible electrically conductive third layer (26) disposed over the second layer. Between the first and the second layers are provided spacers (24) and between the second and the third layers are provided spacers (27). The spacers may be provided by strips of adhesive or by bonding the layers together by welding, for example. The first layer (1) is provided with an array of through apertures (5) each having an inlet (6) facing the second layer (2) and an outlet (7). In response to signals applied to the first and third layers, the second and third layers have portions which are displaced towards the outlets of the apertures by electrostatic forces. The apertures (5) may have conducting walls and the walls may converge.

Abstract: An electrostatic transducer comprises an electrically conductive first layer (1), a flexible insulating second layer (25) disposed over the first layer, and a flexible electrically conductive third layer (26) disposed over the second layer. Between the first and the second layers are provided spacers (24) and between the second and the third layers are provided spacers (27). The spacers may be provided by strips of adhesive or by bonding the layers together by welding, for example. The first layer (1) is provided with an array of through apertures (5) each having an inlet (6) facing the second layer (2) and an outlet (7). In response to signals applied to the first and third layers, the second and third layers have portions which are displaced towards the outlets of the apertures by electrostatic forces. The apertures (5) may have conducting walls and the walls may converge.

Abstract: A class D audio amplifier which provides both an alternating signal and a DC bias voltage to an electrostatic transducer (9). The amplifier comprises an input module (1) for generating a modulated sequence of pulses in response to an input audio signal, and an output module (3) for amplifying the sequence of pulses, which includes high speed switching output transistors (4, 5). A power supply (6) provides a supply voltage to the switching output transistors (4,5). A low pass filter (8) receives the amplified sequence of pulses and generates an output signal for the transducer. The amplified sequence of pulses from the output module (3) is fed to a voltage multiplier module (10) which provides a constant bias voltage for the electrostatic transducer.

Abstract: An electrostatic loudspeaker comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). A signal generator is provided for applying an alternating electrical voltage across the outer layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker. Furthermore at least one of the outer layers (3, 4) is permeable to air displaced by such vibration. Such a loudspeaker can serve as a low cost audio loudspeaker which can be made lightweight and flexible or large-area so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, public-address systems, or in a notebook computer or mobile telephone.

Abstract: An electrostatic loudspeaker comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). A signal generator is provided for applying an alternating electrical voltage across the outer layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker. Furthermore at least one of the outer layers (3, 4) is permeable to air displaced by such vibration. Such a loudspeaker can serve as a low cost audio loudspeaker which can be made lightweight and flexible or large-area so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, public-address systems, or in a notebook computer or mobile telephone.