Adiabatic circuits are low-power electronic circuits which use "reversible logic" to conserve energy. The term "adiabatic" refers to an ideal thermodynamic process in which no heat or mass is exchanged with the surrounding environment, alluding to the ability of the circuits to reduce energy loss as heat. Unlike traditional CMOS circuits, which dissipate energy during switching, adiabatic circuits reduce dissipation by following two key rules: Never turn on a transistor when there is a voltage potential between the source and drain. Never turn off a transistor when current is flowing through it. Because of the second law of thermodynamics, it is not possible to completely convert energy into useful work. However, the term "adiabatic logic" is used to describe logic families that could theoretically operate without losses. The term "quasi-adiabatic logic" is used to describe logic that operates with a lower power than static CMOS logic, but which still has some theoretical non-adiabatic losses. In both cases, the nomenclature is used to indicate that these systems are capable of operating with substantially less power dissipation than traditional static CMOS circuits. History "Adiabatic" is a term of Greek origin that has spent most of its history associated with classical thermodynamics. It refers to a system in which a transition occurs without energy (usually in the form of heat) being either lost to or gained from the system. In the context of electronic systems, rather than heat, electronic charge is preserved. Thus, an ideal adiabatic circuit would operate without the loss or gain of electronic charge. The first usage of the term "adiabatic" in the context of circuitry appears to be traceable back to a paper presented in 1992 at the Second Workshop on Physics and Computation. Although an earlier suggestion of the possibility of energy recovery was made by Charles H. Bennett where in relation to the energy used to perform computation, he stated "This energy could in principle be saved and reused". Principles There are several important principles that are shared by all of these low-power adiabatic systems. These include only turning switches on when there is no potential difference across them, only turning switches off when no current is flowing through them, and using a power supply that is capable of recovering or recycling energy in the form of electric charge. To achieve this, in general, the power supplies of adiabatic logic circuits have used constant current charging (or