A differential amplifier circuit is provided with an operational amplifier and a modulator. The operational amplifier includes a feedback capacitance, and amplifies an analog input signal and outputs an amplified analog output signal. The modulator is connected to a virtual ground point of an input terminal of the operational amplifier, and the modulator switches between a pair of inputted analog differential signals to alternately select one of the analog differential signals based on a predetermined modulation control signal, and outputs a selected analog differential signal. The differential amplifier circuit alternately folds and amplifies the analog input signal within a predetermined input level limit range to generate a signal having different polarities sequentially so as to start from a voltage potential of the virtual ground point at a timing of the modulation control signal. In addition, an converter apparatus is provided with the differential amplifier circuit.