Error correcting apparatus with error corecting signal holding function

摘要

An error signal generating circuit for adjusting a position of a sub-beam on an optical disc to a correct one. A timing circuit generates a test signal so that a driver drives a tracking coil. As a result, a difference signal is generated in a difference signal generating circuit and is then compared to a reference value in a comparing circuit. A controlling signal is generated in a controlling circuit in reply to a comparing error so as to be held in a holding circuit. The thus held controlling signal is converted into an analog signal in a D/A converter and is then applied to a VCA to vary the amplifying rate, such that the difference signal becomes zero when a correct tracking operation is being carried out.