A circuit includes a differential stage configured to provide a differential output signal. An analog-to-digital converter is coupled to first and second output nodes of the differential stage. The analog-to-digital converter is configured to provide an output signal that is a function of the differential output signal from the differential stage. A multiplexer is configured to receive a differential input signal. The multiplexer includes a test switch switchable between a conductive state and a non-conductive state. In the conductive state, the test switch couples the first input node and the second input node of the differential stage. Test signal injection circuitry is activatable to force a differential current through the differential stage. The circuit is selectively switchable between an operational mode and a self-test mode.