US 12,451,849 B2
Audio amplifying circuit and playing device
Yiwei Song, Shanghai (CN); and Tao Zhou, Shanghai (CN)
Assigned to RDA MICROELECTRONICS (SHANGHAI) CO., LTD., Shanghai (CN)
Filed by RDA Microelectronics (Shanghai) Co., Ltd., Shanghai (CN)
Filed on Jun. 25, 2022, as Appl. No. 17/849,599.
Application 17/849,599 is a continuation in part of application No. PCT/CN2020/116583, filed on Sep. 21, 2020.
Application 17/849,599 is a continuation in part of application No. PCT/CN2020/116571, filed on Sep. 21, 2020.
Claims priority of application No. 201922357764.7 (CN), filed on Dec. 25, 2019; and application No. 201922370332.X (CN), filed on Dec. 25, 2019.
Prior Publication US 2022/0329218 A1, Oct. 13, 2022
Int. Cl. H03F 3/213 (2006.01); H03F 3/181 (2006.01); H03F 3/45 (2006.01); H03H 11/12 (2006.01); H03H 19/00 (2006.01)
CPC H03F 3/213 (2013.01) [H03F 3/181 (2013.01); H03F 3/45475 (2013.01); H03H 11/1217 (2013.01); H03H 11/126 (2013.01); H03H 11/1291 (2013.01); H03H 19/004 (2013.01); H03F 2200/03 (2013.01)] 12 Claims
OG exemplary drawing
 
1. An audio amplifying circuit, comprising: N-order filters and an integrated circuit; after an original audio signal passes through the N-order filters, a filtered signal is obtained; after the filtered signal passes through the integrated circuit, a corresponding digital signal is output; wherein a number of operational amplifiers adopted in the N-order filters is smaller than N, and N is a natural number greater than 1;
wherein the N-order filters comprise an (i−1)-th-order filter, and I ranges among 2, 3, . . . , N;
the (i−1)-th-order filter is a first-type filter, wherein the first-type filter comprises: an operational amplifier, a first capacitor and a second capacitor; a positive input end of the operational amplifier is connected to a positive output end of a previous-order filter, a negative input end of the operational amplifier is connected to a negative output end of the previous-order filter, a positive output end of the operational amplifier constitutes a positive output end of the filter, a negative output end of the operational amplifier constitutes a negative output end of the filter, an end of the first capacitor is connected to the positive input end of the operational amplifier, and the other end of the first capacitor is connected to the negative output end of the operational amplifier; an end of the second capacitor is connected to the negative input end of the operational amplifier, and the other end of the second capacitor is connected to the positive output end of the operational amplifier;
wherein the N-order filters further comprise an i-th-order filter; the i-th-order filter is a second-type filter, and
the second-type filter comprises: a third capacitor, a first resistor, a fourth capacitor and a second resistor, an end of the third capacitor is connected to a positive input end of the (i−1)-th-order filter, the other end of the third capacitor is connected to an end of the first resistor, the other end of the first resistor is connected to the positive output end of the (i−1)-th-order filter, an end of the fourth capacitor is connected to a negative input end of the (i−1)-th-order filter, the other end of the fourth capacitor is connected to an end of the second resistor, and the other end of the second resistor is connected to the negative output end of the (i−1)-th-order filter; or, the second-type filter comprises: a third capacitor, a first switched capacitor, a fourth capacitor and a second switched capacitor, an end of the third capacitor is connected to a positive input end of the (i−1)-th-order filter, the other end of the third capacitor is connected to an end of the first switched capacitor, the other end of the first switched capacitor is connected to the positive output end of the (i−1)-th-order filter, an end of the fourth capacitor is connected to a negative input end of the (i−1)-th-order filter, the other end of the fourth capacitor is connected to an end of the second switched capacitor, and the other end of the second switched capacitor is connected to the negative output end of the (i−1)-th-order filter.