Voltage-controlled filter circuit, a semiconductor integrated circuit device for signal processing, and a signal reading apparatus using the circuit and the apparatus
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United States of America Patent
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-
Mar 25, 1997
Grant Date -
N/A
app pub date -
Apr 26, 1995
filing date -
May 12, 1994
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A voltage-controlled filter circuit has a cutoff frequency directly proportional to a ratio of two current values. The filter circuit comprises a variable conductance circuit having two bipolar junction input transistors supplied with an input voltage signal at the bases thereof and a first variable current source at each emitter thereof. The collectors supply the bases of a pair of differential transistors. A second variable current supply is coupled to common emitters of the pair of differential transistors. Externally supplied control signals set the two current values of the variable current sources. The filter circuit may be manufactured as a semiconductor integrated circuit device for signal processing for use in processing a recorded signal read from a recording medium. The recorded signal is supplied to a semiconductor integrated circuit for signal processing to remove unwanted signal and noise components. Specific unwanted signal components may be removed and noise components whose frequencies exceed a cutoff frequency of a low-pass filter provided in a semiconductor integrated circuit are removed.
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