Vtc Inc.

Salman Mazhar

William W Leake

Marius Dina

Graham Teague

An integrated, tuning circuit for tuning a MOSFET-C filter contains a tuning MOSFET and a differential amplifier. A current source is connected to the drain of the tuning MOSFET. The output of the amplifier is coupled to the drain of the tuning MOSFET and to a terminal that connects to the drains of the MOSFETs of the filter, so that the equivalent resistance of the filter is dependant on the current. The current source is coupled to a reference current generator, such that current supplied by the current source to the tuning MOSFET is proportional to the current supplied in the reference current generator, which in turn varies with process and environmental conditions of a capacitance. As a result, changes in process and environmental conditions oppositely affect the capacitance and resistance in the filter, resulting in a fixed RC product and fixed frequency response from the filter.

Automatic-tuning circuit for integrated continuous-time MOSFET-C filters

An apparatus for demodulating two pilot tones for use by a servo control for a magnetic read head is disclosed. The apparatus provides positioning information to position the read head adjacent to a desired information track of a magnetic storage medium. The apparatus comprises a first and a second pilot tone demodulation unit. Each pilot tone demodulation unit comprises a band pass filter for providing a first filtered output signal having an amplitude and a phase representative of the first and the second frequency pilot tones, respectively. A delay lock loop receives the first filtered out of the band pass filter and determines a phase of the frequency pilot tone. A multiplier is connected to the output of the band pass filter and the output of the delay lock loop for multiplying the frequency pilot tone with the output signal of the delay lock loop. A low pass filter is connected to the output of the multiplier for filtering out undesired signals and for passing a DC signal. A comparator is used for comparing the first DC signal to the second DC signal and for determining a position of the magnetic read head with respect to a track of a magnetic storage medium.

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Bloomington, MN, United States of America

Salman Mazhar