Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
2005-01-14
2008-12-02
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
C327S552000
Reexamination Certificate
active
07459963
ABSTRACT:
In a filter apparatus including a master circuit for receiving a reference frequency signal having a reference frequency to generate a control voltage and a slave gm-C filter formed by at least one operational transconductance amplifier and at least one capacitor where the operational transconductance amplifier of the slave gm-C filter is controlled by the control voltage to tune a cut-off frequency or center frequency of the slave gm-C filter, the master circuit is constructed by first and second gm-C filters each formed by at least one operational transconductance amplifier and at least one capacitor and having different frequency characteristics from each other, the first and second gm-C filters being adapted to receive the reference frequency signal, first and second amplitude detectors having inputs connected to outputs of the first and second gm-C filters, respectively, and a differential amplifier having an input connected to outputs of the first and second amplitude detectors and being adapted to amplify a difference-voltage therebetween to generate the control voltage, so that the difference-voltage is brought close to zero.
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Francois Krummenacher, et al., “A 4-MHz CMOS Continuous-Time Filter with On-Chip Automatic Tuning”, IEEE Journal of Solid-State Circuits, vol. 23, No. 3, Jun. 1988, pp. 750-758.
Katsuji Kimura, “An MOS Operational Transconductance Amplifier and an MOS Four-Quadrant Analog Multiplier Using the Quadritail Cell”, IEICE Trans. Fundamentals, vol. E75-A, No. 12, Dec. 1992, pp. 1774-1776.
Le Dinh T.
McGinn IP Law Group PLLC
NEC Electronics Corporation
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