Abstract: An open-loop switching amplifier achieves synchronous operation using a ring oscillator based upon a tapped delay line. A counter is clocked from the ring oscillator, periodically comparing incoming more significant data to the value of the counter to form a pulsewidth modulated output waveform. Modulating the effective width of the output waveform in incremental delay line taps is equivalent to incoming less significant data. This technique then effects time-period summation of coarse and fine resolution clocked data.

Abstract: A method and apparatus for greatly increasing the output voltage or current transformation ratio in an impedance transformation amplifier are disclosed. Broadly, the method takes advantage of multiple, phase-synchronized impedance transformation stages, each of which preferably contributes an equal portion of the eventual output voltage or current.

Abstract: Apparatus and methods for driving multiple output stages with a single switching amplification modulator reduce system cost and complexity. The technique also addresses applications wherein one or more of several output stages of potentially differing output powers are desired at one time. That is, the switching drivers and loads can be the same or different.

Abstract: Feedback for self-calibration of any parameter in an analog and/or digital system is described wherein a system quality factor can be represented by a voltage or current differential. The preferred embodiment is operative to alternately supply two or more optimally equivalent currents or voltages from such a system, detect amplitude and/or phase feedback of resultant output signal at the frequency of the alternation, and use feedback to modify a calibration value, voltage, or current so as to minimize or maximize the feedback, thus effecting self-calibration of the system. Such a method and attendant apparatus enables system self-calibration without need of any high-precision or high-cost components.

Abstract: Centering pulses within the output sample period corrects for instantaneous phase errors in multi-reference switching amplifiers. In the preferred embodiment, the pulses are ordered by the relative magnitude of each switched reference.

Abstract: A method and apparatus are disclosed for inferring amplifier load current from an internal control voltage governing a reference voltage in a multi-reference amplifier. Multi-reference amplifiers typically use internally-regulated references for application to the output stage. In that the output devices of these regulators exhibit limited gain or transconductance, internal voltage variances can be observed as a function of reference load current. This invention solves such problem at negligible additional cost.

Abstract: Apparatus and methods greatly improve AC and, optionally, DC power supply rejection in a switching amplifier. The method broadly includes the steps of modulating the amplifier output with a compensatory signal necessary to maintain a minimum difference between an otherwise unmodulated ancillary reference switching amplifier and a static or dynamic reference.