Common-mode feedback

An electronic device comprising a fully differential amplifier and a common-mode feedback circuit, wherein the fully differential amplifier comprises:

• a positive input terminal and a negative input terminal arranged to receive a differential input voltage thereacross;
• a positive output terminal and a negative output terminal, wherein the fully differential amplifier is arranged to produce a differential output voltage across said output terminals, wherein said differential output voltage is at least partially dependent on said differential input voltage;
• and
• a supply current terminal arranged to receive a tail current for biasing the fully differential amplifier;
• wherein the common-mode feedback circuit comprises first, second, and third transistors, each having a respective drain terminal, source terminal, gate terminal, and back-gate terminal, wherein the common mode feedback circuit is arranged such that:
• the drain terminal of the first transistor and the gate terminals of the first, second, and third transistors are connected together at a bias current terminal;
• the drain terminals of the second and third transistors are connected together at a tail current terminal;
• and
• the source terminals of the first, second, and third transistors are connected together;
• wherein the back-gate terminal of the first transistor is arranged to receive a common-mode reference voltage input, the back-gate terminal of the second transistor is connected to the positive output voltage terminal, and the back-gate terminal of the third transistor is connected to the negative output voltage terminal.