Audio amplifying circuit and playing device

An audio amplifying circuit, comprising:

• N-order filters, a weighting adder, an integrated circuit and a player;
• wherein after a first-path original audio signal passes through the N-order filters, a filtered signal is obtained;
• a second-path original audio signal and the filtered signal are weighted and added through the weighting adder to obtain a weighted addition signal;
• and the weighted addition signal passes through the integrated circuit and the player in sequence to output an audio signal;
• 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.