Area Efficient ADC for Low Frequency Application

Sammanfattning: Analog to digital converters (ADCs) are the fundamental building blocks in communication systems. The need to design ADCs, which are area and/or power efficient, has been common. Various ADC architectures, constrained by resolution capabilities, can be used for this purpose. The cyclic algorithmic architecture of ADC with moderate number of bits comes out to be probably best choice for the minimum area implementation. In this thesis a cyclic ADC is designed using CMOS 65 nm technology. The ADC high-level model is thoroughly explored and its functional blocks are modelled to attain the best possible performance. In particular, the nonlinearities which affect the cyclic/algorithmic converter are discussed. This ADC has been designed for built-in-self-testing (BiST) on a chip. It is only functional during the testing phase, so power dissipation is not a constraint while designing it. As it is supposed to be integrated as an extra circuitry on a chip, its area really matters. The ADC is designed as 10-bit fully differential switch-capacitor (SC) circuit using 65nm CMOS process with 1.2V power supply. A two stage Operational Transconductance Amplifier (OTA) is used in this design to provide sufficient voltage gain. The first stage is a telescopic OTA whereas the second is a common source amplifier. The bottom plate sampling is used to minimize the charge injection effect which is present in the switches.