Amplifiers – With periodic switching input-output
Reexamination Certificate
2003-03-07
2004-08-24
Choe, Henry (Department: 2817)
Amplifiers
With periodic switching input-output
C330S069000
Reexamination Certificate
active
06781450
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of amplifiers, and, in particular, to an auto-zeroed amplifier that is suitable for low frequency applications such as a voltage regulator. The amplifier provides reduced output ripple in voltage regulator applications.
BACKGROUND OF THE INVENTION
An operational amplifier has inherent mismatches that cause an input referred error or offset voltage. A zero differential input voltage will produce a non-zero output because of the mismatches. One solution to this problem is to auto-zero the amplifier using a sampling procedure.
An auto-zero amplifier has two separate phases, an auto-zero phase and an amplifier phase. During the auto-zero phase, the differential input voltages of the operational amplifier is held at a voltage of approximately zero and an output voltage is produced. The output voltage that is produced in the auto-zero phase is stored using capacitors. During the amplification phase, the stored offset voltage is used to correct for the offset on the input to the amplifier.
REFERENCES:
patent: 5124663 (1992-06-01), McEntarfer et al.
patent: 5565813 (1996-10-01), Connell et al.
patent: 6087897 (2000-07-01), Wang
patent: 6198266 (2001-03-01), Mercer
patent: 6400219 (2002-06-01), Fayed
patent: 6639460 (2003-10-01), Botker
Mercer Mark J.
Ranucci Paul
Choe Henry
Darby & Darby P.C.
Gaffney Matthew M.
National Semiconductor Corporation
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