U.S. Philips Corporation

Jozef A M Ramaekers

Joao N V L Ramalho

Johannes O Voorman

Gerben Willem De Jong

Patrick Leclerc

Eric Pieraerts

Marcel Louis Lugthart

Johannes Wm Bergmans

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

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Eindhoven, Netherlands

Jozef A M Ramaekers