High performance amplifier circuits using separate power supplies

A method for providing high supply rejection and rail-to-rail output swing, the method comprising:

• receiving an amplifier input by a first stage to generating a first output, the first stage being powered by a second supply and having a differential input;
• generating an amplifier output by a second stage, the second stage receiving the first output, the second stage being powered by a first supply, the first and second supplies being different in regulation mode;
• and
• coupling a reference voltage to one of the differential inputs of the first stage.

An amplifier comprising, in an integrated circuit:

• a regulator;
• and
• a first stage and a second stage;
• the first stage to receive an amplifier input and to generate a first output, the first stage having a differential input;
• the second stage coupled to the first stage to receive the first output and to generate an amplifier output;
• the second stage and the regulator being powered from a power supply coupled to terminals of the integrated circuit;
• and,
• the first stage being powered by the regulator;
• a reference circuit, the reference circuit being powered by the second supply, one of the differential amplifier inputs being the output of the reference circuit.

An amplifier comprising:

• an integrated circuit having an inverting input including:
• a voltage regulator providing power at a regulated voltage irrespective of voltage variations in power supplied to the voltage regulator;
• and
• an amplifier having a first stage and a second stage;
• the first stage to receive an amplifier input and to generate a first output;
• the second stage coupled to the first stage to receive the first output and to generate an amplifier output;
• the second stage and the regulator both being powered from a power supply coupled to terminals of the integrated circuit;
• and,
• the first stage being powered by the regulator;
• the amplifier further having a gain control feedback element coupled between the amplifier output and the inverting amplifier input.