Patent ID: 7525389

Claim:
A signal amplifier circuit comprising: a negative feedback amplifier circuit comprising an output terminal; first voltage limiting means for limiting output voltage from the negative feedback amplifier circuit; second voltage limiting means for limiting the output voltage from the negative feedback amplifier circuit; a first reference voltage supply for applying a first reference voltage to the first voltage limiting means; a second reference voltage supply for applying a second reference voltage to the second voltage limiting means; wherein the first voltage limiting means is configured to discharge a source current to the output terminal of the negative feedback amplifier circuit when the output voltage from the negative feedback amplifier circuit exceeds the first reference voltage to a lower side, thereby fixing a lower limit saturation voltage at the first reference voltage; and the second voltage limiting means is configured to draw a sink current from the output terminal of the negative feedback amplifier circuit when the output voltage from the negative feedback amplifier circuit exceeds the second reference voltage to a higher side, thereby fixing an upper limit saturation voltage at the second reference voltage.