A low power continuous time band pass sigma delta modulator using linearity enhanced OTA

This paper presents a low power continuous-time bandpass sigma delta modulator for analog to digital converter (ADC) over 5 MHz band. The modulator consists of a fourth order design operating at a Sampling Frequency of 280MHz. The operational transconductance amplifier (OTA) is linearized by using source degeneration technique. This paper investigates the effect of OTA linearization on the modulator performance. It is observed that Signal to Quantization Noise Ratio (SQNR) with a non-linear OTA is of 46.6dB and it is 55.07dB with a Source degenerated OTA showing a marked increase of 1.5 bits(9 dB) in resolution of modulator. Further, optimum transistor sizing leads to a very low power consumption of 10.9mW and a figure of merit of 2.445pJ/bit.