Finite GBW compensation technique for CT ΔΣ modulators with differentiator based ELD compensation

In this work, the mixed-signal differentiator technique for the compensation of excess loop delay has been extended to counteract the effect of the finite GBW of the amplifiers. A RZ DAC is utilized to realize a fast compensation path from the quantizer output to the input of the last integrator. After proper tuning of the scaling coefficients, the original NTF of the modulator can be restored, which has been verified in a 3rd order, single-bit single-loop CT ΔΣ modulator. By using the modified compensation technique, the GBW requirements on the amplifiers can be relaxed significantly while maintaining the SQNR performance and the modulator stability. Consequently, the power consumption of the amplifiers can be drastically reduced.