Full range input/output comparator

A comparator comprising:

• first and second power lines for the application thereto of a first voltage (VP1) and a second voltage (VP2) respectively;
• with VP1 being more positive than VP2;
• first and second differential amplifier stages, each stage having first and second signal input terminals, first and second signal output terminals and first and second power terminals;
• means for coupling the first and second power terminals of said first stage and the first and second power terminals of said second stage between said first power line and said second power line;
• means for applying the same differential input signals across the first and second signal input terminals of said first and second stages;
• said first stage being responsive to differential input signals ranging in value between VP1 and a first voltage level, which is V.sub.T1 volts above VP2, for producing output signals which can swing fully between VP1 and VP2 as a function of the differential input signal;
• said second stage being responsive to differential input signals ranging in value between VP2 and a second voltage level, which is V.sub.T2 volts below VP1, for producing output signals which an swing fully between VP1 and VP2 as a function of the differential input signal;
• where V.sub.T1 and V.sub.T2 are, respectively, first and second threshold voltages;
• and
• means for combining the output signals of said first and second stages for producing output signals which can swing between VP1 and VP2 for values of differential input signals which range between VP1 and VP2.