The quantization noise leakage of the first stage in a MASH21 sigma-delta modulator is analyzed. The results show that the finite DC gain of the opamp is the main reason for noise leakage, and finite GBW and SR only g...The quantization noise leakage of the first stage in a MASH21 sigma-delta modulator is analyzed. The results show that the finite DC gain of the opamp is the main reason for noise leakage, and finite GBW and SR only generate harmonic distortion. The relationship between DC gain and leakage is modeled and conclusions on design criteria are reached. As an example, a MASH21 modulator for a digital audio application is realized. This modulator, fabricated in an 0.18 μm mixed signal process, achieves an SNDR of 91 dB with 1.8 V supply, which verifies the analysis and design criteria.展开更多
This paper introduces a new method for SC sigma-delta modulator modeling.It studies the integrator＇s different equivalent circuits in the integrating and sampling phases.This model uses the OP-AMP input pair＇s tail ...This paper introduces a new method for SC sigma-delta modulator modeling.It studies the integrator＇s different equivalent circuits in the integrating and sampling phases.This model uses the OP-AMP input pair＇s tail current（I_0） and overdrive voltage（v_（on）） as variables.The modulator＇s static and dynamic errors are analyzed.A group of optimized I0 and von for maximum SNR and power x area ratio can be obtained through this model.As examples, a MASH21 modulator for digital audio and a second order modulator for RFID baseband are implemented and tested, and they can achieve 91 dB and 72 dB respectively,which verifies the modeling and design criteria.展开更多
基金supported by the Shenzhen Science and Technology Plan,China(No.QK200610).
文摘The quantization noise leakage of the first stage in a MASH21 sigma-delta modulator is analyzed. The results show that the finite DC gain of the opamp is the main reason for noise leakage, and finite GBW and SR only generate harmonic distortion. The relationship between DC gain and leakage is modeled and conclusions on design criteria are reached. As an example, a MASH21 modulator for a digital audio application is realized. This modulator, fabricated in an 0.18 μm mixed signal process, achieves an SNDR of 91 dB with 1.8 V supply, which verifies the analysis and design criteria.
文摘This paper introduces a new method for SC sigma-delta modulator modeling.It studies the integrator＇s different equivalent circuits in the integrating and sampling phases.This model uses the OP-AMP input pair＇s tail current（I_0） and overdrive voltage（v_（on）） as variables.The modulator＇s static and dynamic errors are analyzed.A group of optimized I0 and von for maximum SNR and power x area ratio can be obtained through this model.As examples, a MASH21 modulator for digital audio and a second order modulator for RFID baseband are implemented and tested, and they can achieve 91 dB and 72 dB respectively,which verifies the modeling and design criteria.
