Patent ID: 7528634

Claim:
A voltage comparator comprising: first and second input terminals to which an input voltage, having a first range of potential variation, is differentially applied; a differential amplifier circuit configured of low voltage devices and high voltage devices, said low voltage devices being unable to sustain a voltage thereacross greater than a second range of variation, said second range being less than said first range, and being connected in a circuit configuration that is operative to perform a differential voltage measurement on said input voltage applied to said first and second input terminals and to provide an output in accordance therewith, said high voltage devices being able to sustain a voltage thereacross of said first range, said high voltage devices being interconnected with said low voltage devices so as to provide high input protective buffering for said low voltage devices, said differential amplifier circuit comprises first and second controlled high voltage input-coupling devices respectively coupled to said first and second input terminals on first and second input voltage-coupling lines, and a folded-cascade differential amplifier containing first and second low voltage transistors connected in differential configuration and having control electrodes thereof respectively coupled by way of first and second low voltage coupling devices to said first and second input voltage-coupling lines, and having output electrodes thereof respectively coupled by way of first and second output-folding high voltage coupling devices to first and second output nodes, and wherein said differential amplifier circuit causes operating levels of said low voltage devices to move up and down with a variation in said input voltage, and thereby prevents application of a voltage across said low voltage devices greater than said second range of variation.