Abstract: Method and apparatus to enable the use of class D amplifiers without the need for an output filter, while maintaining both a high efficiency and a high audio fidelity. Using the classic differential Pulse Width Modulation scheme, the high frequency carrier is first suppressed to achieve a ternary modulation, and then re-introduced as a common mode pulse whose width is modulated to provide the necessary output voltage, but whose width never decreases below a well-defined threshold. The frequency of the modulator waveform (ramp or triangle) may itself be modulated on a sample-by-sample basis, so that the EMI spectrum of the output waveforms can be made white at high frequencies. The combination of the modulation scheme and spread spectrum high frequency behavior allows the user to eliminate the external filter. Various embodiments are disclosed.

Abstract: Method and apparatus to enable the use of class D amplifiers without the need for an output filter, while maintaining both a high efficiency and a high audio fidelity. Using the classic differential Pulse Width Modulation scheme, the high frequency carrier is first suppressed to achieve a ternary modulation, and then re-introduced as a common mode pulse whose width is modulated to provide the necessary output voltage, but whose width never decreases below a well-defined threshold. The frequency of the modulator waveform (ramp or triangle) may itself be modulated on a sample-by-sample basis, so that the EMI spectrum of the output waveforms can be made white at high frequencies. The combination of the modulation scheme and spread spectrum high frequency behavior allows the user to eliminate the external filter. Various embodiments are disclosed.

Abstract: Filterless class D amplifier using spread spectrum pulse width modulation with feedback to suppress low frequency noise in the amplifier output. The amplifiers may use any of a wide variety of pulse width modulators with a dynamically variable frequency ramp or triangular waveform to whiten the output noise of the amplifier. Typically the ramp or triangular waveform input to the modulators is randomly or pseudo randomly varied over some percentage about a nominal frequency. Various feedback techniques for suppressing the low frequency noise are disclosed. Using this invention, Electromagnetic Interference (EMI) emissions from the circuit can be kept substantially below regulatory requirements without the need for expensive external filtering and/or shielding external to the integrated circuit.

Abstract: A multi-step A/D converter of the successive approximation type utilizes a single three-position switchable current-output DAC in combination with a voltage divider, a plurality of comparators, a decoder, a successive approximation register and a control logic module to provide a high speed, high resolution A/D converter requiring fewer parts than the prior art A/D converters of this general type.