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US 9,513,741 B2Granted
Low noise capacitive sensor with integrated bandpass filter
AssigneeTexas Instruments Incorporated
InventorsKaran Singh Jain, Harish Venkataraman
Life of this patent
Estimating the term…
Abstract
A bandpass sense amplifier circuit (FIG. 2A) is disclosed. The circuit includes a capacitor (C0) having a first terminal coupled to receive an input signal (Vin) and a second terminal. A current conveyor circuit (200-206,212) has a third terminal (X) coupled to the second terminal of the capacitor and a fourth terminal (Z) arranged to mirror a current into the third terminal. A voltage follower circuit (214) has an input terminal coupled to the fourth terminal of the current conveyor circuit and an output terminal.
Claims18
A circuit comprising:
- a capacitor having a first terminal coupled to receive an input signal and having a second terminal;
- a current conveyor circuit having a third terminal coupled to the second terminal of the capacitor and having a fourth terminal arranged to mirror a current flowing into the third terminal;
- and
- a first voltage follower circuit having an input terminal coupled to the fourth terminal of the current conveyor circuit and having an output terminal, the voltage follower circuit being configured to reproduce a voltage on the fourth terminal of the current conveyor circuit at the output terminal,
- wherein the current conveyor circuit includes a second voltage follower circuit having the third terminal as an output terminal and having a fifth terminal coupled to receive a reference voltage, and wherein the second voltage follower circuit reproduces the reference voltage at the third terminal.
2 more elements
A touch screen system, comprising:
- a voltage source arranged to produce a drive voltage having a frequency;
- a plurality of first electrodes arranged to selectively receive the drive voltage;
- a plurality of second electrodes proximate the plurality of first electrodes;
- a bandpass sense amplifier selectively coupled to the plurality of second electrodes, the bandpass sense amplifier comprising:
- an input capacitor having a first terminal selectively coupled to the plurality of second electrodes and having a second terminal;
- a current conveyor circuit having a third terminal coupled to the second terminal of the input capacitor and having a fourth terminal arranged to mirror a current flowing into the third terminal;
- and
- a first voltage follower circuit having an input terminal coupled to the fourth terminal of the current conveyor circuit and having an output terminal, the voltage follower circuit being configured to reproduce a voltage on the fourth terminal of the current conveyor circuit at the output terminal,
- wherein the current conveyor circuit includes a second voltage follower circuit having the third terminal as an output terminal and having a fifth terminal coupled to receive a reference voltage, and wherein the second voltage follower circuit reproduces the reference voltage at the third terminal, the touch screen system further comprising:
- an analog to digital converter (ADC) coupled to receive an output signal from the bandpass sense amplifier;
- and
- a processor coupled to receive an output signal from the ADC.
9 more elements
Dependencies are inferred from the claim text.