Patent ID: 6472931
Filing Date: 2002-10-29
Classification: H03K

Abstract:
An apparatus for amplifying an input signal received from a capacitive sensor, comprising:an input that receives an input signal from the capacitive sensor; an amplifier that amplifies the input signal to produce an output signal; a pull-up circuit within the amplifier that pulls the output signal up to a high voltage when the input signal exceeds a threshold voltage; a pull-down circuit within the amplifier that pulls the output signal down to a low voltage when the input signal falls below the threshold voltage; wherein after the output signal is pulled up to the high voltage, the pull-up circuit enters a refractory state in which the pull-up circuit uses a limited current, and the pull-down circuit enters a receptive state in which the pull-down circuit is sensitized to react to small changes in the input signal; wherein after the output signal is pulled down to the low voltage, the pull-down circuit enters a refractory state in which the pull-down circuit uses a limited current, and the pull-up circuit enters a receptive state in which the pull-up circuit is sensitized to react to small changes in the input signal; and an output that makes output signal available to other circuitry.