Koninklijke Philips Corporation N.V.

U.S. Philips Corporation

Patrick Leclerc

Johannes O Voorman

Joao N V L Ramalho

Eric Pieraerts

Lionel Guiraud

Sanjay Manohar Bhandari

Ramesh Selvaraj

Marcel Louis Lugthart

Jozef A M Ramaekers

Jean Barbotin

Fabio Braz

Johannes Wm Bergmans

Fabrice Punch

Joao Nuno V L Ramalho

The invention relates to a switching device comprising programmable compensation means which are associated with the input/output connections for inverting the polarity of the input/output connections when said connections present a polarity inversion which is inherent in the conception of the circuits.

Switching device provided with polarity-inverting means

The present invention relates to an amplifier CD including a first and a second transistor T and T , connected in series between a power supply terminal VCC and ground terminal. According to the invention the transfer terminal of the first transistor T is connected to the bias terminal of the second transistor T and forms an input of the amplifier CD, the bias terminal of the first transistor T being connected to a reference potential terminal. An amplifier CD in accordance with the invention has low input impedance and a low common-mode output level.

Low input impedance with amplifier

A device for reading magnetic information, having at least one read head including at least one magnetoresistive bar MR for generating data pulses representative of information read by the head. To enable the bar to be biased accurately without requiring a measurement of the quiescent resistance of the bar, the device includes a control loop for controlling the power dissipated in the magnetoresistive bar, the control loop having a time constant which is large with respect to the duration of the data pulses.

Device for reading magnetic information

A preamplifier for a multi-head disk drive includes a circuit that tests the connectivity of each magnetic head in the disk drive by driving each head with a small current, and detecting the flow of this current. By driving and sensing the current flowing through the magnetic heads, both open-circuit faults and bridging faults can be detected. In a preferred embodiment, each head is tested sequentially. The result of each test is stored as a bit value in a register, for subsequent access. The circuit may be activated by a test device, or by a microcontroller in an assembled disk drive. To minimize costs, the circuit is integral to the circuitry that is conventionally used to read and write information via the magnetic heads. The oscillator that is conventionally used to characterize the read heads of a disk drive is used in a preferred embodiment to control the sequencing of tests through each head. A very low common mode voltage is provided during the testing of each write head, to minimize ESD (electro-static discharge) related problems. In a test mode, each write head is selected after a read head is selected, thereby minimizing the possibility of an accidental corruption of the data when the write head is tested. To avoid a degradation of performance, and in particular a degradation of rise/fall times in the write driver, the circuitry that controls the test voltages and currents is provided substantially up-stream of the write driver.

Magnetic head conductivity testing and form factor determination in a read/write device

An arrangement is disclosed for reading information from a record carrier. The arrangement comprises a read head having at least one magneto-resistive element (R,), a first transistor (Tr,) and a second transistor (Tr,). The base of the first transistor (Tr,) is coupled to the emitter of the second transistor (Tr,) via a first capacitor (,). The base of the second transistor (Tr,) is coupled to the emitter of the first transistor (Tr,) via a second capacitor (,). The arrangement further comprises a non-linear transconductance amplifier (,) having first and second inputs coupled to the output terminals (,) of the arrangement, and having and inverting and non-inverting outputs coupled to the bases of the first and second transistor. The non-linear transconductance amplifier (,) is adapted to supply a control current at its inverting and non-inverting outputs in response to a voltage present across its inputs, such that for first and second input voltages resulting in first and second output currents, respectively, the first input voltage being larger than the second input voltage, the amplification factor of the transconductance means being larger for generating the first output current than for generating the second output current.

Arrangement for reading information from a magnetic record carrier

The invention relates to a system for reading magnetic information, comprising a magnetoresistive bar and a first differential amplifier connected to the magnetoresistive bar. A reading system according to the invention also comprises a second differential amplifier arranged in parallel with the first amplifier, a first capacitor arranged between the first transistor and the magnetoresistive bar, and a second capacitor arranged between the fourth transistor and the bar, and an analog adder combining the output signals of the first and second amplifiers. This structure allows integration of the decoupling capacitors and thus prevents the occurrence of external resistances and inductances which are detrimental to the common-mode reject rate.

Integrated system for reading magnetic information

An 'H' type amplifier circuit uses at least two current mirrors for alternately feeding current into the load in one direction and the other direction. In order to accelerate the turn-on of the current mirrors, a capacitance is associated with each of the two current mirrors. Each capacitance is alternately coupled in parallel with the input of its associated current mirror when this current mirror delivers current, and is coupled to the supply voltage terminals when this current mirror delivers no current. The operation is effected by means of a set of switches.

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Caen, France

Patrick Leclerc