Composite differential direct-coupled instrumentation amplifier
AssigneeNeff Instrument Corporation
InventorWilliam R. Chambers
Life of this patent
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Abstract
A differential amplifier which utilizes a pair of wideband operational amplifiers as output stages for two differential output signals, a pair of high performance DC operational amplifiers to buffer input signals to the pair of wideband operational amplifiers used as output stages and reduce offset voltage error by the amount of the DC gain of the pair of high performance DC operational amplifiers, apparatus for biasing the pair of high performance DC operational amplifiers to provide exceptional DC characteristics and eliminate common mode response from those amplifiers, and apparatus for feeding forward high frequency AC input to the wideband operational amplifiers operating as the output stages without loading the common mode input impedance of the differential amplifier.
Claims11
A differential instrumentation amplifier comprising a pair of wideband operational amplifiers as output stages for two differential output signals, a pair of high performance DC operational amplifiers to buffer input signals to the output operational amplifiers and reduce offset voltage error by the amount of their DC gain, means for biasing the pair of high performance DC operational amplifiers to provide precision DC characteristics and eliminate common mode responses from the high performance DC operational amplifiers, and means for feeding forward high frequency AC input to the wideband operational amplifiers operating as output stages while eliminating common mode voltages in the high frequencies, in which the means for biasing the pair of high performance DC operational amplifiers to provide precision DC characteristics and eliminate common mode response from the high performance DC operational amplifiers comprises first and second floating voltage sources for applying voltage levels to each of the high performance DC operational amplifiers, means joining one terminal of each of the first and second floating voltage sources associated with each high performance DC operational amplifier to a biasing terminal of the high performance DC operational amplifier, and means for varying the voltage level at a second terminal of the first and second floating voltage sources to match a level at a non-inverting input to the associated amplifier.
A differential instrumentation amplifier comprising a pair of wideband operational amplifiers as output stages for two differential output signals, a pair of high performance DC operational amplifiers to buffer input signals to the output operational amplifiers and reduce offset voltage error by the amount of their DC gain, means for biasing the pair of high performance DC operational amplifiers to provide precision DC characteristics and eliminate common mode responses from the high performance DC operational amplifiers, and means for feeding forward high frequency AC input to the wideband operational amplifiers operating as output stages while eliminating common mode voltages in the high frequencies, in which the means for feeding forward high frequency AC input to the wideband operational amplifiers operating as output stages comprises a capacitor joining a non-inverting input terminal of each of the high performance DC operational amplifiers with a non-inverting input terminal of each of the output operational amplifiers.
A differential instrumentation amplifier comprising a pair of wideband operational amplifiers as output stages for two differential output signals, a pair of high performance DC operational amplifiers to buffer input signals to the wideband output operational amplifiers and reduce offset voltage error by the amount of the DC gain of the wideband amplifiers, and means for biasing the pair of high performance DC operational amplifiers to provide precision DC characteristics and eliminate common mode responses from the high performance DC operational amplifiers, the means for biasing including first and second floating voltage sources for biasing each of the high performance DC operational amplifiers, means joining one terminal of each of the first and second floating voltage sources associated with each high performance DC operational amplifier to a biasing terminal of the high performance DC operational amplifier, and means for varying the voltage level at a second terminal of the first and second floating voltage sources to follow an input signal level at an input to the associated high performance DC operational amplifier.
Dependencies are inferred from the claim text.