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US 4,542,304 AGranted
Switched capacitor feedback sample-and-hold circuit
AssigneeAT&T Bell Laboratories
InventorEric J. Swanson
Life of this patent
Estimating the term…
Abstract
The feedback sample-and-hold stages of a transversal filter bank include a primary sample-and-hold branch and a secondary sample-and-hold branch for correction of offset voltage in the primary branch which results from switching charge feedthrough of its sampling switch. A pair of N-channel buffer transistors, one an enhancement type and one a depletion type, are so connected to the branches that power supply noise is attenuated. Additionally, the parasitic capacitance of the enhancement transistor acts as a coupling capacitor for the correction function.
Claims4
A sample-and-hold circuit apparatus of the type comprising:
- an amplifier having an inverting input port, a noninverting input port, and an output port;
- a buffer, comprising an enhancement mode transistor having a gate electrode which forms an input port of said buffer and having a drain-to-source conduction path which at one side forms an output port of said buffer;
- a sampling switch connected between a signal input and the input port of said buffer;
- a holding capacitor connected at a first side to the input port of said buffer and at a second side to a reference potential;
- a feedback means connected to the output port of said buffer and coupled to an input port of said amplifier;
- a correction switch connected at a first side to the output port of said amplifier;
- a correction holding capacitor connected at a first side to a reference potential and at a second side to a second side of said correction switch, and
- means coupling a second side of said correction switch to the drain of said enhancement mode transistor.
5 more elements
Dependencies are inferred from the claim text.