Low voltage operational amplifier input stage and method

A method for providing an amplified output signal from an input stage of a low voltage operational amplifier, the method comprising the steps of:

• applying a differential input signal to gates of a differential pair of N-channel depletion-mode metal oxide semiconductor field effect transistors (MOSFETs);
• and
• providing the amplified input from drain outputs of the differential pair of N-channel depletion-mode MOSFETs based on saturation currents of the differential pair of N-channel depletion-mode MOSFETs.

A low voltage operational amplifier input stage comprising:

• a first N-channel depletion-mode metal oxide semiconductor field effect transistor (MOSFET) having a source terminal, a drain terminal, and a gate terminal, wherein the drain terminal of the first N-channel depletion-mode MOSFET provides a first output signal;
• and
• a second N-channel depletion-mode MOSFET having a source terminal, a drain terminal, and a gate terminal, wherein the source terminals of the first and second N-channel depletion-mode MOSFETs are commonly coupled to form a differential pair, the gate terminals serve as the differential inputs of the differential pair, and the drain terminal of the second N-channel depletion-mode MOSFET provides a second output signal.