Trap filter and low pass filter

Abstract

The invention discloses a trap filter which comprises a first integrating circuit, a unit gain anti-phase circuit and a second integrating circuit. An input terminal of the first integrating circuit is an input terminal of the trap filter, an output terminal of the second integrating circuit is an output terminal of the trap filter, a feedforward capacitor connects the input terminal with a feedback input terminal of the second integrating circuit, a feedback resistor and a feedback capacitor are in parallel connection between the output terminal and a feedback input terminal of the first integrating circuit, and a current control circuit connects the first integrating circuit with an anti-phase input terminal of an operational amplifier in the second integrating circuit. The invention also discloses a low pass filter, wherein an integrating circuit has a same structure of the above trap filter. An integrator has a large time constant, using a large resistor and a large capacitor can be avoided, and integration becomes simple.

Description

【Technical field】 [0001] The invention relates to an integrated circuit, in particular to a notch filter in the integrated circuit, and also to a low-pass filter. 【Background technique】 [0002] In analog circuit design, notch filters are usually used to suppress or eliminate specific frequency interference. Because power frequency (50Hz or 60Hz) interference is ubiquitous, many instruments and equipment (such as ECG monitors, etc.) contain traps to suppress this power frequency interference. [0003] This notch filter is generally welded on a printed circuit board (PCB) with discrete resistors, discrete capacitors and operational amplifiers. However, the notch filter formed by soldering PCB in this way not only has high power consumption and large volume, but also has low precision. [0004] Integrating all the traps in one chip can eliminate the problems of the traps mentioned above. However, in modern microelectronics technology, the resistance integrated in the chip g...

AI Technical Summary

Problems solved by technology

However, in modern microelectronics technology, the resistance integrated in the chip generally does not exceed 500KΩ, and the capacitance does not exceed 50pF. This is because if the integrated resistance or integrated capacitance exceeds these values, their nonlinearity will greatly damage the performance of the circuit, and the gain outweighs the gain.

Under such limitations, the center frequency of the notch filter cannot meet the requirements for suppressing power frequency interference

[0005] The integrated filter also has the above-mentioned filter frequency control problem

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