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US 4,890,066 AGranted
Envelope detector
AssigneeU.S. Philips Corporation
InventorsWillibrordus G. M. M. Straver, Ernst H. Nordholt
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AssigneeU.S. Philips Corporation
InventorsWillibrordus G. M. M. Straver, Ernst H. Nordholt
Estimating the term…
Envelope detector comprising a differential amplifier (A), a full-wave rectifier circuit and a smoothing filter (AF), which differential amplifier (A) converts an input voltage into a pair of current signals in phase opposition and which full-wave rectifier circuit comprises a pair of half-wave rectifiers (HWR1, HWR2) for half-wave rectifying the said pair of current signals, coupled to a first combining stage (S) for combining the output signals of the two half-wave rectifiers (HWR1, HWR2) with like polarity, which first combining stage (S) supplies a full-wave rectified signal. In order to reduce d.c. offsets, the detector comprises a frequency-dependent negative feedback loop which comprises a second combining stage (D) coupled to the outputs (R.sub.o1, R.sub.o2) of the pair of half-wave rectifiers (HWR1, HWR2) for combining the output signals of the pair of half-wave rectifiers (HWR1, HWR2) with opposite polarity, said second combining stage (D) being negatively fed back to the input (I.sub.c) of the differential amplifier (A) via a low-pass filter (LPF) for a selection of the d.c. component.
An envelope detector comprising a differential amplifier, a full-wave rectifier circuit and a smoothing filter, said differential amplifier converting an input voltage into a pair of current signals in phase opposition, said full-wave rectifier circuit comprising a pair of half-wave rectifiers for half-wave rectifying the said pair of current signals and furnishing respective half-wave rectifier output signals corresponding to the so-rectified current signals, and a first combining stage coupled to said full-wave rectifier circuit for combining said half-wave rectifier output signals with like polarity, characterized by a frequency-dependent negative feedback loop which has a second combining stage coupled to the outputs of the pair of half-wave rectifiers for combining said half-wave rectifier output signals with opposite polarity, said second combining stage being negatively fed back to the differential amplifier via a low-pass filter for a selection of the d.c. component.
Dependencies are inferred from the claim text.