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This paper presents a single-bit fifth-order continuous-time sigma-delta modulator for UMTS application. To relax the linearity requirement of the first integrator, a low-pass filter is inserted in the negative feedback loop after the summing node. To reduce power consumption, the loop- filter is implemented using a feed-forward topology. Measurement results show that it achieves 62 dB SNDR with an over-sampling ratio of 32 over a 2 MHz bandwidth. The power consumption is 8 mW at a supply voltage of 2.5 V in a 1-poly 5- metal 0.24 mum CMOS technology.
Date of Conference: 2-5 July 2007