The paper deals with nonlinear dynamic circuits containing MOS transistors. The problem of global and local stability of a class of these circuits is considered in detail. It is shown that any circuit belonging to this class is Lagrange stable. In a special case where no independent sources act in the circuit, it is proved that the origin is the only equilibrium point and the circuit is globally asymptotically stable. Special attention has been paid to the circuits driven by dc sources, having multiple equilibrium points. A simple tool for proving asymptotic stability of equilibrium points is developed and illustrated by numerical examples.