A 0.5-V Wideband Amplifier for a 1-MHz CT Complex Delta-Sigma Modulator

This brief presents a fully differential wideband amplifier for 0.5-V supply. The amplifier employs a gate-input two-stage topology and a DC common-mode feedback circuit with a Miller-amplified capacitor for frequency compensation. Designed in a 130-nm triple-well complementary metal-oxide-semiconductor process with regular
VT
transistors, the amplifier achieves a simulated performance of 51-dB DC open-loop gain, 112-MHz unity gain bandwidth, and 67deg phase margin with a load of 6.5 pF/19.6 kOmega , and consumes 600 muW at 0.5-V supply. The proposed amplifier is incorporated in a continuous-time complex delta-sigma modulator with a 1-MHz signal bandwidth and 64times oversampling ratio. In the simulations, the modulator achieves a 72.5-dB signal-to-noise-plus-distortion ratio and consumes 2.3 mW at 0.5 V.