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Elimination of Feedthrough in Transducers

IP.com Disclosure Number: IPCOM000090082D
Original Publication Date: 1969-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Heidecker, RF: AUTHOR [+2]

Abstract

This circuit eliminates feedthrough noise between write and read heads in a multitrack transducer by a feed forward technique.

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Elimination of Feedthrough in Transducers

This circuit eliminates feedthrough noise between write and read heads in a multitrack transducer by a feed forward technique.

Each centertapped write coil 20 of write heads 22 in the transducer is connected to a separate write driver. Each output coil 24 of corresponding read heads 26 is connected to a separate read amplifier. During simultaneous reading and writing operations, substantial feedthrough noise is transmitted from the write heads into the read amplifier. Much of this noise is eliminated by this circuit. A feedforward circuit, including a resistor 28, is connected to one side of each write coil 20. The several feedforward circuits are tied in common through capacitor 30 to the base of emitter-follower transistor 32. The output of the emitter-follower is coupled through capacitor 34 to a distributing network of resistors 36. These supply feedthrough noise cancelling inputs to the several read amplifiers.

Each feedforward circuit 28 receives a signal when its associated coil is energized. This signal, as passed by capacitor 30, is a pulse whose polarity depends upon which write coil side the feedforward circuit 28 is coupled with. By proper selection of connecting points, the composite signal is made to have a polarity opposite to the feedthrough noise. The coil side selected is the same for all tracks in the transducer, so no personalizing is necessary from track to track or transducer to transducer. The time...