An amplifier circuit including a first amplifier having a first amplifier input and a first amplifier output and a transformer including a first transformer component having a first primary winding in series with the first amplifier output and a first secondary winding coupled to the first amplifier input. The first primary winding and the first secondary winding are arranged such that a portion of a first magnetic field generated by the first primary winding couples to the first secondary winding through a first magnetically coupled feedback loop. The transformer further includes a second transformer component having a second primary winding in series with an output of a second amplifier and a second secondary winding coupled to an input of the second amplifier input. A portion of a second magnetic field generated by the second primary winding couples to the second secondary winding through a second magnetically coupled feedback loop.

An integrated circuit device includes a digital-to-analog converter with multiple bit slices, each bit slice having a differential pair of driver transistors. A driver circuit includes the differential pairs of driver transistors, multiple series cascode transistors, and current bleed paths to modify drain-to-source currents in the various cascode transistors. Additional embodiments include series peaking circuits, back termination networks, and neutralization capacitors. Other embodiments are disclosed.