Apparatus for converting an AC component of a signal to a square wave

An apparatus responsive to an input signal that is indicative of a rotation of a rotor of a motor for generating a square wave output signal that is indicative of said rotation of said rotor, comprising:

• a sensor coupled to said rotor for generating said input signal containing an AC component superimposed on an offset component;
• an operational amplifier responsive to said signal components of said input signal for generating an output signal of said amplifier;
• a feedback network coupled to said amplifier for establishing a predetermined small signal closed-loop gain in said amplifier to control an amplitude of said output signal of said amplifier;
• a capacitor;
• switching means for coupling in a feedback manner said output signal to said capacitor to develop in said capacitor a voltage that is coupled to a first input terminal of said amplifier at a magnitude that is determined in accordance with said offset component;
• and
• a comparator responsive to an output signal of said amplifier and to said input signal for generating said square wave signal in accordance with a difference therebetween, wherein said feedback network comprises a first resistor coupled between an output terminal of said amplifier and said first input terminal of said amplifier and said capacitor is coupled in series with said first resistor such that said first input terminal is coupled between said capacitor and said first resistor.

An apparatus for converting a sinusoidal signal superimposed on DC offset component to a square wave signal, comprising;

• a source of said sinusoidal signal;
• an operational amplifier having a noninverting input terminal coupled to said source of said sinusoidal signal and responsive to said sinusoidal signal for amplifying said sinusoidal signal;
• a feedback network for establishing a closed-loop signal gain of said operational amplifier including a first resistor coupled to said operational amplifier between an output terminal and an inverting input terminal of said operational amplifier and a series arrangement of a second resistor and a capacitor that is coupled between said inverting input terminal and a common conductor;
• a pair of diodes coupled in an anti-parallel manner between said capacitor and said output terminal of said operational amplifier;
• and
• a comparator having a noninverting input terminal that is coupled to one of said source of said sinusoidal signal and to said output terminal of said operational amplifier and having an inverting input terminal that is coupled to the other one of said source of said sinusoidal signal and said output terminal of said amplifier for generating said square-wave signal at an output terminal of said comparator.