A circuit for converting a charge signal into a binary format of output bits comprises: an integration circuit including an operational transconductance amplifier having an inverting input terminal and an output terminal, an integrating capacitor connected between the inverting input terminal and the output terminal, the integrating capacitor for storing a charge input selectively provided by a sensor diode; and a folding circuit having a fold capacitor, the fold capacitor switchably coupled either to a fold voltage source via a fold buffer for charging the fold capacitor to a predetermined fold charge value, or to the integrating capacitor for selectively removing at least a portion of the stored charge input.