US Patent No. 9,287,839


Patent No. 9,287,839
Issue Date March 15, 2016
Title Feedback Loop For Direct Current (dc) Offset Removal
Inventorship Christophe Jean-Francois Amadi, Austin, TX (US)
Jason Lee Wardlaw, Austin, TX (US)
Emmanuel A. Marchais, Dripping Springs, TX (US)
Dylan Alexander Hester, Austin, TX (US)
Daniel John Allen, Austin, TX (US)
John Christopher Tucker, Austin, TX (US)
Assignee CIRRUS LOGIC, INC., Austin, TX (US)

Claim of US Patent No. 9,287,839

1. An apparatus, comprising:
an input node configured to receive an input signal;
an amplifier comprising a first amplifier input node, a second amplifier input node, and an amplifier output node, wherein
the first amplifier input node is coupled to the input node; and

a feedback loop coupled to the second amplifier input, wherein the feedback loop is configured to adjust a first common mode
of the input signal to control a second common mode of an output signal at the amplifier output node, wherein the feedback
loop comprises a mixed-signal servo loop and wherein the feedback loop is configured to:

perform digital loop tracking through a digital low-pass filter (LPF) and a digital integrator; and
perform analog loop tracking through the digital low-pass filter (LPF), the digital integrator, a direct current (DC) modulator,
and a digital-to-analog converter (DAC).