Apparatus and method for receiving high-common mode voltage range signals with low-voltage devices

摘要

An input stage employs low-voltage MOSFETs as input devices for an operational amplifier circuit that operates at common mode voltages that may exceed the gate-oxide breakdown voltage of the input devices. Also, the input stage is arranged for relatively low noise. The input stage is arranged to detect the input common mode voltage and to feed back the detected input common mode voltage to a base of a bipolar folded cascode transistor that is coupled to the drain of the input devices. Accordingly, the input devices are bootstrapped such that they are protected from gate-oxide breakdown.