Back to results
US 7,843,258 B2Granted
Filter circuit
AssigneeRicoh Company, Ltd.
InventorKazuhisa Ishiguro
Life of this patent
Estimating the term…
Abstract
A plurality of low-pass filters (2-1, 2-2, 2-3) are cascaded to the post stage of an OTA (1) and a plurality of high-pass notch filters (3-1, 3-2, 3-3) are cascaded further to the post-stage thereof so that a high-pass filter having a Q is not connected to the output of the OTA (1) having a high output impedance and a capacitor having a low capacitance is not connected with the output of th OTA (1) thus preventing multifeedback and avoiding such problems as the zero point of the notch filter (BEF) deviates from a design value or oscillation takes place.
Claims3
A filter circuit, comprising:
- a current output type buffer amplifier;
- and
- a plurality of low-pass notch filters and a plurality of high-pass notch filters which are cascaded to a post-stage of the buffer amplifier,
- wherein the low-pass notch filter is connected at least immediately after the buffer amplifier, and a high-dimensional band-pass filter is constructed by cascading the plurality of low-pass notch filters and the plurality of high-pass notch filters, and
- wherein the plurality of low-pass notch filters are cascaded to a post-stage of the buffer amplifier, and the plurality of high-pass notch filters are cascaded to a post-stage of the plurality of low-pass notch filters.
2 more elements
Dependencies are inferred from the claim text.