In this paper, we propose a new architecture for analog-to-digital converters (ADCs) using multistate spatial wavefunction-switched field-effect transistors (SWSFETs). SWSFETs are multiple quantum coupled well devices, where the wells are stacked vertically and the electron wavefunction switches from one well to another with the change in gate voltage. Quantum mechanical simulations of 3-well InGaAs-AlInAs SWSFET structures are presented. The designs and simulations of 2-bit and 3-bit ADCs using SWSFETs result in low power consumption and reduced device count which improves the speed of the data conversion.