Differential circuits with constant gm bias

A different amplifier device comprising:

• an output resistor;
• a first switch comprising a first gate and a first drain and a first source, the first gate being coupled to a first voltage input;
• a second switch comprising a second gate and a second drain and a second source, the second gate being coupled to a second voltage input, the second drain being coupled to the output resistor;
• a voltage supply;
• a feedback circuit comprising a third switch and a fourth switch and a first amplifier, the third switch and the fourth switch being coupled to the voltage supply;
• a first common resistor and a second common resistor coupled to the feedback circuit;
• a bias generator circuit configured to provide a bias reference voltage to the feedback circuit;
• and
• a current source coupled to the second drain and the first voltage input.

A different amplifier device comprising:

• a first switch comprising an NMOS transistor having a first gate and a first drain and a first source, the first gate being coupled to a first voltage input;
• a second switch comprising an NMOS transistor having a second gate and a second drain and a second source, the second gate being coupled to a second voltage input;
• a feedback circuit comprising a third switch and a fourth switch and a first amplifier;
• a first common resistor and a second common resistor coupled to the feedback circuit;
• a bias generator circuit being coupled to the voltage supply and the feedback circuit, the bias generator circuit being configured to provide a bias reference voltage to the feedback circuit;
• and
• a current source comprising a fifth switch and a second amplifier, inputs terminals of the second amplifier being coupled to the second drain and the first voltage input.