Amplifier, fully-differential amplifier and delta-sigma modulator

A fully-differential amplifier, comprising:

• a front-end gain stage, having a first terminal and a second terminal outputting a differential signal that has been amplified by the front-end gain stage;
• a first AC-coupled push-pull output stage, comprising:
• a first transistor, having a source, a drain and a gate, wherein the source of the first transistor is coupled to a first voltage level;
• a second transistor, having a source, a drain and a gate, wherein the source of the second transistor is coupled to a second voltage level, the gate of the second transistor is coupled to the first terminal of the front-end gain stage, and the drain of the second transistor is coupled to the drain of the first transistor to form a first output terminal of the fully-differential amplifier;
• and
• a first AC-coupled capacitor, coupled between the first terminal of the front-end gain stage and the gate of the first transistor;
• and
• a second AC-coupled push-pull output stage, comprising:
• a third transistor, having a source, a drain and a gate, wherein the source of the third transistor is coupled to the first voltage level;
• a fourth transistor, having a source, a drain and a gate, wherein the source of the fourth transistor is coupled to the second voltage level, the gate of the fourth transistor is coupled to the second terminal of the front-end gain stage, and the drain of the fourth
• transistor is coupled to the drain of the third transistor to form a second output terminal of the fully-differential amplifier;
• and
• a second AC-coupled capacitor, coupled between the second terminal of the front-end gain stage and the gate of the third transistor;
• wherein the fully-differential amplifier outputs a differential output signal via the first and second output terminals.