A current sense device includes a reference transistor for electrically coupling to a power transistor, a sense transistor for electrically coupling to the power transistor, and control circuitry. Thecontrol circuitry is configured to (a) control current through the sense transistor such that a voltage at the sense transistor has a predetermined relationship to a voltage at the power transistor,and (b) control current through the sense transistor according to one or more operating conditions at the reference transistor, to compensate for aging of the power transistor.