Filter apparatus including slave gm-C filter with frequency...

Details Filter apparatus including slave gm-C filter with frequency... Filter apparatus including slave gm-C filter with frequency...

2007-02-20

2007-02-20

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

11045358

ABSTRACT:
In a filter apparatus includes a master circuit receiving a reference frequency to generate a control voltage, and a slave gm-C filter for receiving an input voltage to generate an output voltage. The slave gm-C filter is controlled by the control voltage to adjust the cut-off frequency or center frequency of the slave gm-C filter. The master circuit is a PLL circuit including a phase shifter receiving a reference frequency signal to change the phase of the reference frequency signal, a phase comparator to generate a phase error signal, and a loop filter adapted for excluding an AC component signal from the phase error signal to generate a DC component thereof. As a result, this DC component signal is supplied as the control voltage to the phase shifter and the slave gm-C filter.

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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, pp. 950-958, Jun. 1988.

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