U.S. Philips Corporation

Hendrik J Pothast

Johannes O Voorman

Ho W Wong-Lam

Johannes W Bergmans

A device for write precompensation of data signals to be recorded on a magnetic medium, which device has an input for receiving input data signals and an output for supplying output signals to be recorded, an integrator/limiter circuit which receives the input data signals and which supplies an output signal which is in synchronism with the data signal and whose amplitude varies substantially linearly as a function of time at positions where a signal transition appears in the data signal, which amplitude is limited within a data symbol interval; an adjustable filter which receives the input signals and supplies an output signal whose instantaneous values depend on the pattern of preceding and future signal transitions in the data signal; and a comparator circuit which through comparison of the output signal of the integrator/limiter circuit and the output signal of the filter produces the output signal in which at least some signal transitions of the input data signal can be shifted in time. An important aspect of the present invention is that with the output signal dt an arbitrary number of desired time shifts can be obtained rather than that, as in the prior art, only a choice can be made from a limited number of delay values.

Device for write compensation in magnetic media recording

A recording apparatus including a magnetic write head and a write amplifier with capacitive current compensation. The write amplifier is made up of four current mirrors which are turned on two at a time by two switchable floating current sources connected between the input terminals of the current mirrors in order to produce a write current of alternating polarity through the write head. The parasitic capacitances across the write head and/or the parasitic capacitances of the write amplifier at the write terminals are neutralized by means of neutralizing capacitors. The high impedance at the terminals of the write head enables the common-mode voltage across the write head to be fixed at any desired voltage value by means of a common-mode circuit.

Arrangement comprising a magnetic write head, and write amplifier with

An apparatus for recording on a magnetic record carrier includes a write amplifier comprising four current mirrors which are turned on two at a time by two switchable floating current sources connected between the input terminals of the current mirrors in order to produce a write current of alternating polarity through a write head. The high impedance at the terminals of the write head enables the common-mode voltage across the write head to be fixed at any desired voltage value by means of a common-mode circuit. The symmetrical structure further enables the parasitic capacitances at the write terminals to be neutralized by means of neutralizing capacitors.

Magnetic head write amplifier including current mirrors and switchable

A differential amplifier comprises a Darlington differential pair (T.sub.1 /T.sub.3, T.sub.2 /T.sub.4) and a cross-coupled transistor pair (T.sub.5, T.sub.6) to increase the transconductance of the Darlington differential pair (T.sub.1 /T.sub.3, T.sub.2 /T.sub.4). The negative input impedance of the differential amplifier as a result of the presence of the cross-coupled differential pair (T.sub.5, T.sub.6) is compensated for at high frequencies and the gain of the differential amplifier is reduced by a compensation circuit with a capacitor (30) between the control electrodes of the transistors of the cross-coupled differential pair (T.sub.5, T.sub.6) and with resistors (26, 28) in series with the control electrodes of the transistors of the cross-coupled differential pair (T.sub.5, T.sub.6).

Growing community of inventors

Eindhoven, Netherlands

Hendrik J Pothast