Operational amplifiers having low-power unconditionally-stable common-mode feedback

An amplifier circuit, comprising:

• first and second resistors configured to receive first and second input voltages respectively;
• and
• an operational amplifier, comprising:
• a first transistor coupled to the first resistor;
• a second transistor coupled to the second resistor, wherein the first and second transistors form a differential pair;
• a current steering module coupled to first and second transistors and configured to sense an output common-mode voltage of the operational amplifier;
• and
• a current source configured to provide a current and coupled to the first and second transistors and the current steering module;
• wherein the first transistor, second transistor, and current steering module are configured such that a portion of the current is steered from the current steering module or to the current steering module based on common-mode voltages of the first and second input voltages and a common-mode output voltage of the amplifier circuit voltage to set the common-mode output voltage.