U.S. Philips Corporation

Koninklijke Philips Corporation N.V.

Joao N V L Ramalho

Johannes O Voorman

Eric Pieraerts

Gerben Willem De Jong

Patrick Leclerc

Jozef A M Ramaekers

Jean Barbotin

Marcel Louis Lugthart

Luan Le

Johannes Wm Bergmans

Mareel L Lugthart

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 recording apparatus for recording an information signal on a magnetic record carrier includes a write driver circuit and a magnetic write head. The write driver circuit comprises a first voltage driver and a second voltage driver. A first current driver and a second current driver are present for driving the write head. The first and second voltage driver each include a respective series circuit of an npn transistor and a bidirectional impedance element coupled between a point of constant potential and the respective outputs of the first and second voltage drivers.

Recording apparatus provided with a write driver circuit

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

A device for measuring the resistance of an MR element which passes a bias current Imr and which derives a bias voltage. A voltage comparator CMP receives the bias voltage Vmr and a reference voltage Vref. A counter UPCNT has an enable input EN coupled to the output of the comparator and a digital output forming the output of the device. A current source supplies the bias current Imr which represents a digital value received by the current source at its control input which is coupled to the digital output of the counter. The device enables the digital value of a resistance to be measured automatically.

Apparatus for automatic measurement of resistance of integrated MR device

An apparatus for detecting peaks of positive and negative polarity in an information signal. The apparatus comprises a first peak detector means for detecting the positive peaks and a second peak detector for detecting the negative peaks. The first peak detector means comprises a first capacitor, and has an attack time for charging the first capacitor (,) and a decay time for discharging the first capacitor, the attack time being shorter than the decay time. The first peak detector has an output for generating an output signal (,) having a first output signal value when the first peak detector is in a charging state for charging the first capacitor and having a second output value when the first peak detector is in a non-charging state. The first peak detector maintains the first capacitor charged at a first level (V,) during time intervals that the information signal level is below said first level, said first level being larger than the zero signal level and the first peak detector is further in the charged state when the information signal level exceeds the charging level of the first capacitor. The second peak detector means comprises a second capacitor, and has an attack time for charging the second capacitor and a decay time for discharging the second capacitor, the attack time being shorter than the decay time. The second peak detector has an output (,) for generating an output signal having a third output signal value when the second peak detector is in a charging state for charging the second capacitor and having a fourth output value when the second peak detector is in a non-charging state. The second peak detector is adapted to maintain the second capacitor charged at a second level (V,) during time intervals that the absolute value of said information signal level is below said second level, said second level being larger than the zero signal level. The second peak detector is further in the charged state when the absolute value of the information signal level exceeds the charging level of the second capacitor.

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Bieville-Beuville, France

Joao N V L Ramalho