An IC includes a plurality of pads at a top surface of a semiconductor wafer, an amplifier configured to receive a first AC signal at an input terminal, and output a second AC signal at an output terminal, a first detection circuit coupled to the input terminal and configured to output a first DC voltage to a first pad of the plurality of pads responsive to the first AC signal, and a second detection circuit coupled to the output terminal and configured to output a second DC voltage to a second pad of the plurality of pads responsive to the second AC signal.