Differential mode circuitry and method of calibrating same without matched external current sources

摘要

A common mode feedback circuit includes first and second nodes defining a differential node pair. A collective plurality of transconductors includes a first plurality of transconductors associated with the first node and a second plurality of transconductors associated with the second node. Each plurality, for example, may consist of 2 transconductors such that one may be serve as a common mode current sink and the other may be operated as a current source during calibration. At least one transconductor of the collective plurality has an adjustable transconductance. In various embodiments, each node has at least one transconductor with an adjustable transconductance. The common mode feedback circuit includes a calibration engine. The calibration engine adjusts at least one adjustable transconductor until a sensed differential voltage across the differential node pair is substantially zero without the use of external current sources.