We show that the nonlinearity of the first integrator's operational transconductance amplifier(OTA) significantly degrades the alias rejection of a bandpass CT∆ΣM in the presence of OTA parasitics. We derive the expression for alias rejection when the OTA used in the first integrator is realized as a two stage feed-forward compensated structure. Simulation results confirm the theory. © 2019 IEEE

Shanthi Pavan Y

Department of Electrical Engineering

Saravana Manivannan

Bandpass amplifiers

Bandpass filters

Continuous time systems

Band pass

CONTINUOUS-TIME BANDPASS

DELTA-SIGMA CONVERTERS

FEED FORWARD

LOOP FILTER

Parasitics

Operational amplifiers

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IIT Madras

Degradation of Alias Rejection in Continuous-Time Bandpass Delta-Sigma Converters due to Weak Loop Filter Nonlinearities

Proceedings - IEEE International Symposium on Circuits and Systems

Implicit anti-aliasing is a remarkable property of continuous-time delta-sigma modulators employing a time-invariant loop filter. It turns out that weak nonlinearity of the operational transconductance amplifier (OTA) used in the input integrator, in conjunction with the DAC pulse shape and OTA parasitics can greatly degrade the alias rejection of the modulator. The authors report and analyze this hitherto undiscovered mechanism. The theory is borne out by measurement results from a fourth-order single-bit filtering delta-sigma modulator designed in a 65-nm CMOS process. The alias-rejection of the modulator, which is expected to be about 160dB, is degraded to around 70dB by weak OTA nonlinearity and OTA parasitics. © 2004-2012 IEEE.

IEEE Transactions on Circuits and Systems I: Regular Papers

Degradation of Alias Rejection in Continuous-Time Delta-Sigma Modulators by Weak Loop-Filter Nonlinearities

IEEE Journal of Solid-State Circuits

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Degradation of alias rejection in continuous-time bandpass delta-sigma converters due to weak loop filter nonlinearities

Journal	Data powered by TypesetProceedings - IEEE International Symposium on Circuits and Systems
Publisher	Data powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN	02714310
Open Access	No