Abstract: A hearing aid uses multiple compression feedback loops to minimize sound distortion includes a preamplifier network having an input connected to an input receiver, an output, and an automatically adjustable gain. The preamplifier network measures an output signal which is preferably a voltage and automatically adjusts the gain in response to the output signal. The hearing aid also includes an output drive network having an input connected to the preamplifier network output and an output connected to a load, such as a transducer. The output drive network has an automatically adjustable gain which is responsive to a measured signal at the output of the network. A volume control circuit may also be connected between the output of the preamplifier network and the input of the output drive network to permit the person wearing the hearing aid to adjust the output volume.

Abstract: An amplifier uses gain compression techniques to provide linear gain control over a wide dynamic range, and includes an amplifier having input and output legs, a gain controller coupled between the input and output legs of the amplifier, a gain control circuit having an input coupled to the amplifier output leg and output coupled to the gain controller. The gain controller is responsive to a gain control signal to permit continuous gain adjustment of the amplifier. The gain control circuit is configured to compare an output voltage on the amplifier output leg with a predetermined threshold voltage and to generate a gain control signal on the gain control circuit output so as to provide continuous gain adjustment of the amplifier at least when the amplifier output voltage is greater than the threshold voltage. A hearing aid using a single compression amplifier or multiple compression amplifiers to minimize sound distortion and enhance user comfort is also provided.

Abstract: A delay circuit for differential signals has input terminals for receiving primary and complementary phases of the differential signals and output terminals upon which the primary and complementary phases of output differential signals are generated after a suitable delay. A differential comparator controls charging and discharging of first and second capacitors, one capacitor being provided for each phase for providing a seleced delay. The time difference between switching of the differential comparator and the subsequent voltage level transistion of the relative charges on the first and second capacitors determines the time delay dt. The delay circuit is compensated for power supply and temperature variation.

Abstract: An integrated, high speed, zero hold current and delay compensated charge pump operable at one of two different selectable pumping currents. The charge pump includes first and second supply terminals, a first input terminal for receiving digital charge-up control signals, a second input terminal for receiving digital charge-down control signals, and an output terminal. A first transistorized differential amplifier controls a first current flow of a first polarity between the first supply terminal and the output terminal as a function of the charge-up control signals. A second differential amplifier controls a second current flow between the first and second supply terminals as a function of the charge-down control signals. A pump current mirror produces a mirrored second current flow of a second polarity between the output terminal and the second supply terminal as a function of the second current flow.

Abstract: An integrated circuit phase-locked loop includes a bipolar bandwidth switch for selectively coupling circuit elements of an external bandwidth filter network so as to control loop bandwidth. The bandwidth switch includes first and second switched terminal means which are coupled to the bandwidth filter network. A differential amplifier has a first control terminal coupled to the first switched terminal and a second control terminal coupled to the second switched terminal. The differential amplifier controls first and second currents as a function of a difference between potentials applied to the first and second switched terminals. A first current mirror couples the differential amplifier to the second switched terminal and controls current flow between a first supply terminal and the second switched terminal as a function of the first current.