Patent ID: 7154423
Filing Date: 2006-12-26
Classification: H03M

Abstract:
1. A successive approximation analog-to-digital converter comprising a comparator for sequentially comparing an analog input voltage with a comparison voltage to generate a comparison result, wherein said comparator comprises: a first inverter for receiving the analog input voltage and the comparison voltage in sequence; a capacitor having one plate connected to said first inverter to store an electric charge; a second inverter connected to another plate of said capacitor; a first feedback switch connected in parallel to an input and an output terminal of said first inverter; and a second feedback switch connected in parallel to an input and an output terminal of said second inverter, said first feedback switch including first and second transistors connected in parallel to each other to the input and output terminals of said first inverter, said first transistor being formed to have a driving capacity larger than that of said second transistor, said second feedback switch including third and fourth transistors connected in parallel to each other to the input and output terminals of said second inverter, said third transistor being formed to have a driving capacity larger than that of said fourth transistor, said first and third transistors having respective gate electrodes connected to each other and further connected to a first control input terminal for receiving a first control signal, said second and fourth transistors having respective gate electrodes connected to each other and further connected to a second control input terminal for receiving a second control signal, in successive approximation operation, said first and third transistors being controlled differently in timing of switching between conductive and non-conductive states from said second and fourth transistors to compare the analog input voltage with the comparison voltage.