Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Patent
1993-05-19
1995-09-12
Psitos, Aristotelis
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
360 29, 360 51, 360 7702, G11B 509, G11B 502, G11B 5596
Patent
active
054502497
ABSTRACT:
A demodulator circuit receives an input signal read from a track of a magnetic medium and generates a control signal to maintain alignment of a read-write head with the track. The demodulator circuit includes at least one transistor. The at least one transistor has an electrode switchable between first and second voltage sources. The electrode is coupled to the second voltage source to block processing of the input signal. The electrode is coupled to the first voltage source to process the input signal. The at least one transistor provides an effective resistance when coupled to the first voltage source that is dependent on the voltage level of the first voltage source. The at least one transistor half-wave rectifies the input signal when the electrode is coupled to the first voltage source. In this manner, the at least one transistor provides an effective resistance when the electrode is coupled to the first voltage source, the magnitude of the effective resistance being determined by the voltage level of the first voltage source, half-wave rectifies the input signal, and simultaneously selects that portion of the input signal to rectify. Disk drive systems that utilize this technique have the advantage of at least one transistor simultaneously selecting the number of pulses to be integrated when turned on and blocking integration of the input signal when turned off, controlling the gain of an integrator by varying the resistance when turned on, and half-wave rectifying the incoming signal to vary the automatic gain control.
REFERENCES:
patent: 4669004 (1987-05-01), Moon et al.
patent: 5187619 (1993-02-01), Sidman
patent: 5319508 (1994-06-01), Tsunoda et al.
Nagaraj Krishnaswamy
Shariatdoust Reza S.
American Telephone and Telegraph Company
Kim Won Tae C.
Psitos Aristotelis
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