Texas Instruments Corporation

Texas Instruments Denmark

Texas Instruments, Copenhagen Aps

Niels Anderskouv

Lars Risbo

Thomas Morch

In a method and an amplifier for the compensation of unlinearities e.g. of the class D type, wherein an audio signal is pulse-width modulated, e.g. with a carrier wave signal in the form of a triangular signal to provide a pulse-width modulated small-signal, the so-called multiplicative error signals, which occur prior to the provision of a pulse-width modulated great-signal (), are detected in a detector ()). It is noted that the carrier wave signal could be analog as well as digital. The signal from the detector, which is derived on the basis of differences between the pulse widths of the small-signals and the pulse widths of the great-signals, is used for changing the carrier wave signal so that the amplifier gets a constant gain in the entire audio range and is thereby linearized. To compensate additionally for the multiplicative errors which manifest themselves in the pulse height as well as the pulse width of the pulse-width modulated great-signal (), the value of the carrier wave signal is changed as a function of the pulse-width modulated small-signal () multiplied by the pulse-width modulated great-signal and the inverted pulse-width modulated small-signal multiplied by the inverted pulse-width modulated great-signal.

Method in the compensation of unlinearities in an amplifier, and uses of the method and the amplifier

A method and apparatus of measuring current in a switching circuit ( ) of the two-port type having a first set of terminals connected to a set of terminals of a noise reducing circuit, wherein a second set of terminals of the switching circuit has a switching terminal, which is adapted to be switched between the set of terminals of the noise reducing circuit, including the steps of providing an impedance in parallel with the switching circuit; measuring a current as a transient measurement during switching sequences in the switching circuit, the measurement being performed across an impedance in the noise reducing circuit.

Method of reducing distortion and noise of square-wave pulses, a circuit for generating minimally distorted pulses and use of method and circuit

According to the invention, a method and an amplifier e.g. of the class D type, in particular connected as class BD, wherein an audio signal is pulse-with modulated in that two sets of switches are adapted to make and break signal paths transferring pulses representing the non-inverted or inverted part of the audio signal, comprise attenuating noise and zero crossing distortion which occur because of crosstalk between modulator and control circuit halves in the amplifier. Noise and zero crossing distortion are attenuated by delaying the pulses which represent the non-inverted part and the inverted part, respectively, of the audio signal relative to each other, when the audio signal is in the vicinity of the value 0, thereby achieving modulation of the audio signal which contains characteristics from pulse with modulation of both class AD and BD type. The advantage of this is that at low signal levels the amplifier obtains the linear properties of the class AD amplifiers at zero crossing and the low noise of the class BD amplifier. The pulse-with modulation type is here called class ABD.

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Niels Anderskouv