A low power second order sigma-delta modulator (ΣΔM), for biomedical applications, has been presented in this paper. This can be used to digitize electrical biomedical signals like Electro-cardiogram (ECG) Electroencephalogram (EEG), and
Electroretinogram (ERG). The proposed sigma delta modulator has been implemented by Switched Capacitor (SC) technique. Behavioral modeling of nonideal second order SC ΣΔM was done to find out the integrator's opamp specifications to attain resolution of 10 bits. Integrator has been designed to minimize distortion and charge injection, and remove input dependent offset voltage. Dynamic latched comparator has been employed for power reduction. The feedback circuit has been designed for minimum usage of switches and capacitors. The simulated results of the proposed ΣΔMin standard CMOS 0.18 µm technology, using Tanner tools gives > 10 bits resolution and power consumption ranges from 50 µW to 400 µW with a 1.8 V power supply.

Keywords: Biomedical application,SDToolbox, Second Order Sigma-delta modulator.