Tunable filter with gain control circuit

Details Tunable filter with gain control circuit Tunable filter with gain control circuit

2011-08-09

2011-08-09

Chang, Joseph (Department: 2817)

Oscillators

With synchronizing, triggering or pulsing circuits

C331S018000, C331S002000

Reexamination Certificate

active

07994870

ABSTRACT:
An apparatus includes a filter and a gain control circuit. The filter receives and filters an input signal and provides an output signal in a first mode and operates as part of an oscillator in a second mode. The gain control circuit varies the amplitude of an oscillator signal from the oscillator in the second mode, e.g., by adjusting at least one variable gain element within the oscillator to obtain a target amplitude and/or non rail-to-rail signal swing for the oscillator signal. The apparatus may further include a bandwidth control circuit to adjust the bandwidth of the filter in the second mode. The bandwidth control circuit receives the oscillator signal, determines a target oscillation frequency corresponding to a selected bandwidth for the filter, and adjusts at least one circuit element within the filter to obtain the target oscillation frequency.

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Durharn A M et al: “Low-distortion Continuous-time Integrated CMOS Filters for the Audio-DSP Interface” Consumer Electronics, 1992. Digest of Technical Papers. ICCE., IEEE 1992 International Conference on Rosemont, IL, USA Jun. 2-4, 1992, New York, NY, USA, IEEE, US, pp. 92-93, XP010102922.
International Search Report and Written Opinion—PCT/US2009/061386, International Search Authority—European Patent Office—Jan. 29, 2010.

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