Time dependence of the charge equilibration (fill-and-spill) input technique for profiled peristaltic charge-transfer devices

A simple closed-form mathematical model is derived for the time-limited spill mechanism in charge equilibration inputs on profiled peristaltic charge-transfer devices (CTD's). Two modes of operation, peak detection and signal sampling, are analyzed representing extremes in the time variation of the input signal relative to the CTD clock. The theoretical models indicate two linear regions of the input-output curve characterized by thermal-diffusion-dominated transport and self-induced drift-dominated transport, respectively. These linear regions are clearly visible in the experimental data. By drawing straight lines through these data, the necessary model parameters are easily derived and these, in turn, give physical quantities such as thermal diffusion coefficient and surface doping. The numbers obtained in this fashion are a good indication of the model's validity when compared to independent measurements. Additional verification is provided by the accurate prediction of the output versus spill time curve at a single input level based on the parameters obtained by matching the model to the experimental input-output curve for one spill time. Theoretical curves are presented to illustrate the dependence on input gate geometries and spill time. Finally, isolines of time-dependent nonlinearity are plotted versus input voltage and spill time to aid in locating the sufficiently linear operating region.