Low-voltage fully differential switched-opamp bandpass EA modulator

The paper deals with the design of a low-voltage bandpass ZA modulator implemented with the switched-capacitor technique. To use standard technology (no low-threshold devices) and without an on-chip voltage multiplier, the switched-opamp technique has been adopted. The basic building blocks for the construction of a IA modulator (SC integrator, quantiser, and feedback DAC) are proposed in a fully differential version. In addition, they have been improved with respect to those previously reported to give a larger output swing at a higher sampling frequency and without any voltage reference. The validity of the proposed circuits is demonstrated by the realisation of a secondorder bandpass ZA modulator operating with a single IV supply within a standard 0.5um CMOS technology (VTIJn= 0.65V, VTIlp = 0.7V). The modulator operates at a sampling frequency of 1.8MHz with a full-scale input range of 2Vpk.pk and achieves a 45dB dynamic range in a 20kHz bandwidth