Patent ID: 7994954

Claim:
A circuit for obtaining a calibrated output signal from an input signal, the circuit comprising: an analogue gain amplifier comprising a first input for receiving said input signal, said analogue gain amplifier being configured to apply a gain to said input signal; an analogue to digital converter for converting said input signal to digital form after amplification by said gain amplifier; a correction circuit for receiving a signal derived from the output of the analogue to digital converter and outputting a digital offset signal; and a digital to analogue converter for receiving said digital offset signal and feeding a corresponding analogue offset signal back to said first input of said gain amplifier, such that said correction circuit and said digital to analogue converter form a feedback loop applying an offset to said input signal prior to amplification, wherein said correction circuit includes an inverse gain circuit for applying an inverse gain to a signal within said correction circuit prior to said digital to analogue converter.