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Magnetic Head Write Driver

IP.com Disclosure Number: IPCOM000073621D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Chaloupka, JA: AUTHOR [+2]

Abstract

A fast rise time is obtained with a low-voltage circuit by switching the current through an inductor. Data is written by reversing the "on" and "off" status of one of transistors T4 and T5 to pass current through one or the other of the head coils L3 or L4 and the inductor L2. Since, at each reversal, current is already flowing through the inductor L2 and one of the head coils, an essentially instantaneous current is available to the other head coil. Two modes of operation are possible; one is an uncompensated normal mode (for example: NRZI) and the other is a pulse-crowding compensation mode (used, for example, in phase encoding). In mode 1, resistor R is shunted to give high current operations by turning transistor T3 on. In mode 2, resistor R remains in the circuit to give lower current operations.

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Magnetic Head Write Driver

A fast rise time is obtained with a low-voltage circuit by switching the current through an inductor. Data is written by reversing the "on" and "off" status of one of transistors T4 and T5 to pass current through one or the other of the head coils L3 or L4 and the inductor L2. Since, at each reversal, current is already flowing through the inductor L2 and one of the head coils, an essentially instantaneous current is available to the other head coil. Two modes of operation are possible; one is an uncompensated normal mode (for example: NRZI) and the other is a pulse-crowding compensation mode (used, for example, in phase encoding). In mode 1, resistor R is shunted to give high current operations by turning transistor T3 on. In mode 2, resistor R remains in the circuit to give lower current operations. Initially, in mode 2, transistor T2 is on giving a current pulse amplitude I1 (through L2) plus I2 (through L1). After time t = d, single-shot SS turns transistor Tl on and transistor T2 off to essentially instantaneously reduce the pulse amplitude to I1.

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