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Write Current Stabilizer for Multielement Magnetic Head

IP.com Disclosure Number: IPCOM000080122D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Ainscow, F: AUTHOR

Abstract

In a multiple head file, common write driving circuitry may be used to avoid duplication of circuitry for each head. If the file bit rate is high, the driving circuitry must be connected to the heads by matched transmission lines to avoid distortion of the write current. Where the head is a multielement thin-film head, there is the additional problem of a considerable variation in resistance between the individual transducing elements. Since the resistance of thin-film elements is comparable with the matching impedance of the line, there can be considerable variation in the write currents of different head elements.

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Write Current Stabilizer for Multielement Magnetic Head

In a multiple head file, common write driving circuitry may be used to avoid duplication of circuitry for each head. If the file bit rate is high, the driving circuitry must be connected to the heads by matched transmission lines to avoid distortion of the write current. Where the head is a multielement thin-film head, there is the additional problem of a considerable variation in resistance between the individual transducing elements. Since the resistance of thin-film elements is comparable with the matching impedance of the line, there can be considerable variation in the write currents of different head elements.

A circuit is shown for controlling write current to a head transducing element H, connected between two sections L1 and L2 of a split transmission line. It is to be understood that element H is one of a number of such elements, not shown, any of which may be connected into the transmission line by appropriate switching circuitry, not shown.

The element H is driven by switching driving current alternately through transistors T1 and T2, to produce a current Iw at the element. When T1 is off, for example, current flows from ground through RL1, along L1, through element H and back along line L2 to T2 collector. Since all the head current Iw must flow in terminating impedance RL1, the voltage at point A is exactly equal to Iw RL1 after the switching transient is over. Similarly, during the alternate h...