AC differential amplifier with reduced low corner frequency

An AC amplifier comprising:

• a pair of transconductance stages, each transconductance stage comprising
• first and second outputs respectively connected to the first and second outputs of the other transconductance stage and forming a pair of output nodes for the AC amplifier,
• first and second inputs, with the first input of each transconductance stage forming an input terminal for the AC amplifier,
• a differential pair of transistors, each transistor comprising first and second conduction terminals and a control terminal, the second conduction terminals being connected together at a common current node, the control terminals respectively forming the first and second inputs of the AC differential amplifier, and the first conduction terminals respectively forming the first and second outputs of the AC differential amplifier, and
• a current generator connected to the common current node for biasing said differential pair of transistors;
• a shunt capacitor connected in-line with the common current node and between the second conduction terminal of each transconductance stage;
• a pair of load resistors connected between a voltage reference and respectively connected to the pair of output nodes;
• and
• at least one capacitor connected between the second inputs of said pair of transconductance stages.

A method for forming an AC amplifier comprising:

• connecting a pair of differential transconductance stages together, each transconductance stage comprising
• first and second outputs respectively connected to the first and second outputs of the other transconductance stage and forming a pair of output nodes for the AC amplifier, and
• first and second inputs, with the first input of each transconductance stage forming an input terminal for the AC amplifier;
• connecting a pair of load resistors between a voltage reference and the pair of output nodes;
• and
• connecting at least one capacitor between the second inputs of the pair of differential transconductance stages, wherein the at least one capacitor comprises a pair of identical capacitors connected in series and forming an intermediate node therebetween, with the intermediate node being connected to a second voltage reference.

A method for forming an AC amplifier comprising:

• connecting a pair of differential transconductance stages together, each transconductance stage comprising
• first and second outputs respectively connected to the first and second outputs of the other transconductance stage and forming a pair of output nodes for the AC amplifier,
• first and second inputs, with the first input of each transconductance stage forming an input terminal for the AC amplifier,
• a differential pair of transistors, each transistor comprising first and second conduction terminals and a control terminal, the second conduction terminals being connected together at a common current node, the control terminals respectively forming the first and second inputs of the AC differential amplifier, and the first conduction terminate respectively forming the first and second outputs of the AC differential amplifier, and
• a current generator connected to the common current node for biasing said differential pair of transistors;
• connecting a shunt capacitor in-line with the common current node and between the second conduction terminal of each transconductance stage;
• connecting a pair of load resistors between a voltage reference and the pair of output nodes;
• and
• connecting at least one capacitor between the second inputs of the pair of differential transconductance stages.