In view of the problem that ΣΔ modulator implemented in analog circuits is limited by the amplitude of input signals,this paper designed a second-order ΣΔ modulator based on a Field Programmable Gate Array( FPGA) data expansion method. The modulator can accurately modulate full-scale signals; in addition,for the waveform output,a simple passive filter can be used to realize the filtering of quantizing noise and the demodulation of signal. Compared with the simulated circuit,the FPGA can realize the effectiv...