Amplifiers – Signal feedback – At least one push-pull signal stage
Reexamination Certificate
2006-11-13
2008-09-09
Choe, Henry K (Department: 2817)
Amplifiers
Signal feedback
At least one push-pull signal stage
C330S075000
Reexamination Certificate
active
07423480
ABSTRACT:
A front-end circuit suitable for digital multimeters and measurement devices may be configured with strictly capacitive attenuators replacing the resistive attenuators in the AC signal path. An inverting programmable-gain amplifier (PGA) may be built around an operational amplifier (op-amp), with a single resistor for DC feedback providing a 1st-order response for AC coupling. The single resistor may be replaced by a more complex RC network to provide a 2nd-order response. The feedback circuit may also include active components such as additional op-amps, which may assist in shaping the overall response and/or reducing the DC offset at the output of the circuit. The capacitive load presented to the input by the front-end circuit may be minimized to compare to capacitances present in resistive implementations. The circuit would not present a DC load to the input since DC loads are typically the result of a resistive attenuator in the DC signal path.
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Choe Henry K
Hood Jeffrey C.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
National Instruments Corporation
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