An apparatus for the open-loop or closed-loop control of the composition of the mixture desired in the combustion chamber of an internal combustion engine, which includes an exhaust gas sensor whose output signal together with other operational parameters, determines the mixture composition. The essential component of the apparatus is a storage unit with which charging and discharging sources controllable in accordance with the sensor signal are associated, wherein the magnitude of the charging and discharging signal is dependent on operational parameters. The storage unit may comprise a capacitor or a resistor-capacitor combination having one terminal connected to ground and another terminal efficiently connected with an operational voltage connection, so as to have in this manner an unequivocal association with a fixed potential.