Input impedance biasing

A method, comprising:

• providing an impedance at an intermediate bias node, wherein the impedance is provided with a bias circuit that comprises:
• a first transistor coupled to a first power supply;
• and
• a second transistor coupled to a second power supply,
• wherein a gate of the first transistor is coupled to a gate of the second transistor at the intermediate bias node, and
• wherein the first transistor and the second transistor provide a selected DC impedance at the intermediate bias node between the first power supply and the second power supply;
• low-pass filtering, with the impedance provided at the intermediate bias node, noise from a terminal at which a direct current (DC) signal is applied;
• and
• high-pass filtering, with the impedance provided at the intermediate bias node, a signal from a terminal at which an alternating current (AC) signal is applied.

An apparatus, comprising:

• an audio controller configured to perform steps comprising:
• providing an impedance at an intermediate bias node, wherein the impedance is provided with a bias circuit that comprises:
• a first transistor coupled to a first power supply;
• and
• a second transistor coupled to a second power supply,
• wherein a gate of the first transistor is coupled to a gate of the second transistor at the intermediate bias node, and
• wherein the first transistor and the second transistor provide a selected DC impedance at the intermediate bias node between the first power supply and the second power supply;
• low-pass filtering, with the impedance provided at the intermediate bias node, noise from a terminal at which a direct current (DC) signal is applied;
• and
• high-pass filtering, with the impedance provided at the intermediate bias node, a signal from a terminal at which an alternating current (AC) signal is applied.