A 4-bit 1.356 Gsps ADC for DS-CDMA UWB System

In this paper, a 4-bit 1.356GS/S analog to digital (A/D) converter targeted for the direct spectrum code division multiple access ultra wide band (DS-CDMA UWB) is presented. The A/D converter uses a fully differential flash architecture. To achieve low power consumption and high conversion rate, the proposed converter is designed with current mode amplifier (CMA) and each preamplifier includes a dual sense amplifier (DSA). The A/D converter can sample input frequencies above 650 MHz with this current mode processing technique. The A/D converter achieves 3.7 effective number of bits (ENOBs) for a 30MHz sinusoidal input and 3.35 ENOBs for a 650 MHz input at a 1.356 GHz sampling rate. At 1.356 GS/s, the current consumption is 38 mA including digital logic with a power supply of 1.8V. The proposed A/D converter is fabricated using a 0.18-mum 6Metal lPoly CMOS process and the active area is 0.35 mm².