The automatic compensation of zero-drift errors in direct-coupled feedback systems

It is shown first that a degenerative feedback produces no improvement in the zero-drift errors of direct-coupled amplifiers. A method is described whereby these errors can be reduced to any desired amount by the use of an auxiliary amplifier. A single auxiliary amplifier, by means of suitable switching, can be used to correct continuously the balance of a number of main feedback systems. The effects of the balancing circuits on stability are discussed with particular reference to the case where the feedback system is a position-control servo-mechanism.