Key words:A low power second order sigma-delta modulator (ÓÄM), for biomedical applications, has been presented in this paper. This can be used to digitize electrical biomedical signals like , , and Electroretinogram (ERG). The proposed sigma delta modulator has been implemented by Switched Capacitor (SC) technique. Behavioral modeling of nonideal second order SC ÓÄM 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 ÓÄM in 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.Biomedical application, SD Toolbox, Second Order Sigma-delta modulator. Electro-cardiogram (ECG) Electroencephalogram (EEG)

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Key words:Floating point (FP) representation is commonly used to represent real numbers. Some papers have suggested the use of logarithmic number system (LNS) in addition to floating point. In LNS, a real number is represented as a fixed point logarithm. Therefore multiplication and division in LNS are much simpler in comparison to that in FP, so the LNS can be beneficial if addition and subtraction can be performed with speed and accuracy equal to FP. LNS addition and subtraction requires interpolation technique for which some vales are stored in read only memory (ROM). In this paper, different sizes of ROM are used for addition and subtraction and their performances are compared to the floating point.FPGA, Logarithmic Number Systems, ROM.