Amplifier having improved common mode voltage range

Abstract

Embodiments of the invention include an amplifier such as a differential amplifier having an improved common mode voltage range (CMVR). The amplifier includes a translator coupled to a second stage amplifying circuitry wherein the translator uses feedback and a parallel connection of input devices to improve the common mode voltage range of the amplifier while providing for enablement of the circuit functionality. The translator uses parallel connections of N-channel and P-channel devices such as transistors to extract alternating current (ac) signals riding on a common mode voltage and to translate the extracted ac signals to ride on a constant reference voltage (V.sub.ref). The translated signals are then amplified in a conventional manner, such as by a gate thresholding or a self-biasing technique. An input sensing circuit within the translator provides an offset detection signal to a correction circuit, also within the translator. The correction circuit compares the signal with an applied reference signal (V.sub.ref) and, based thereon, applies a correction signal to the input sensing circuit. With the benefit of such correction signals, the input sensing circuit translates an input signal with a large common mode voltage range to an output signal that rides on the dc voltage that is approximately equal to the reference signal, V.sub.ref.