| 摘要 |
In an amplifier including an AC amplifier, its operation level shifts according to input waveforms. This invention describes a circuit to eliminate the level shift. An output of the AC amplifier is fed to a level shift detector, wherein the level shift is detected to provide an error signal to a pulse width modulation circuit. In this circuit, a pulse of a pulse width corresponding with the level shift is generated and fed to a preamplifier, wherein the input waveform and the pulse are synthesized to be fed back to the AC amplifier. This feed back loop clamps a zero level of the input waveforms.
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