US Patent 7616938 Mixer offset cancellation without generating I/Q imbalance

An offset cancellation scheme in which offset cancellation current is sourced into one differential branch of a driver circuit and sinked from the opposite differential branch. The source/sink arrangement allows for offset cancellation current to be introduced into the circuit, but the overall total average current remains substantially unchanged. When used in an I and Q mixer circuits, the offsets may be canceled without generating an I/Q imbalance in the I and Q mixers.