Switch-Induced Error Voltage on a Switched Capacitor

A concise arrafytical expression for switch-induced error voltage on a switched capacitor is derived from the distributed MQSFET model. The result, however, can be interpreted in terms of a simple lumped equivalent circuit. With this expression we explore the dependence of the error voltage on process, switch turnoff rate, source resistance, and other circuit parameters. These results can be used to qnic$fy predict the error voltage. The analytical expression is supported by the close agreement with computer simulations and experiments. B CL co~ c c: G L L~ N sub R~ t ; VG VH VL vVT v vd~t ) ‘dn ‘dm w LIST OF SYMBOLS Conductance coefficient Storage capacitance Gate-drain overlap capacitance Gate capacitance (excluding overlap capacitance) Gate capacitance per unit area Channel conductance Effective channel length (L~,.W, – 2L~) Lateral diffusion distance Substrate doping Source resistance of the signal voltage source Gate-oxide thickness Gate voltage falling rate Gate voltage High value of V~ Low value of V~ Signal voltage at the source Threshold voltage with back-gate bias Zero-bias threshold voltage Error voltage at drain end at time t Error voltage at drain end after gate voltage reaches V~ Absolute value Of vd~ Channel width.