A sensor comprises a first transistor comprising a first control terminal, a second transistor that is a scaled version of and connected to the first transistor and comprising a second control terminal, an operational amplifier connected to both the first and second transistors and configured to generate an intermediate signal at an output terminal, a variable current source, a current mirror, a measurement circuit, and a chopper circuit. The first and second control terminals are configured to receive a drive signal. The variable current source is configured to generate a first variable current as a function of the intermediate signal. The current mirror configured to apply a second variable current proportional to the first variable current to the second transistor. The measurement circuit is configured to generate a measurement signal indicative of current through the first transistor. The chopper circuit is configured to shift an offset of the operation amplifier.