Operation amplification circuit, active electrode and electric physiological signal acquisition system

Abstract

The invention provides an operation amplification circuit. The operation amplification circuit is composed of four NMOS (N-channel Metal Oxide Semiconductor) tubes, five P type common-source and common-grid tubes, an N-type common-source and common-grid tube, a first resistor and a first capacitor, wherein differential input pair tubes are composed of two NMOS tubes with large grid electrode areas; an inverted input end and an in-phase input end are composed of grid electrodes of the NMOS tubes. The invention further provides an active electrode with the operation amplification circuit, and an electric physiological signal acquisition system with the active electrode. By virtue of the operation amplification circuit and the active electrode circuit, signal amplification with relatively greater gain can be realized on the electrode by the electric physiological signal acquisition system; the anti-interference capability of a physiological signal is effectively enhanced, noises are reduced and the signal precision is enhanced; meanwhile, the operation amplification circuit has a larger input resistance (much higher than skin resistance); on one hand, the problem in the prior art that a skin cleaning agent and conductor glue are needed can be solved; on the other hand, the signal acquisition precision can also be improved.

Description

technical field [0001] The invention relates to the field of analog integrated circuits, in particular to an operational amplifier circuit, an active electrode and an electrophysiological signal acquisition system. Background technique [0002] In the actual measurement of physiological signals such as ECG and EEG, skin cleansers and conductor glue are usually used to reduce skin impedance and enhance the conductivity between electrodes and skin. However, this traditional measurement method usually requires a long preparation time and will cause a certain degree of damage to the human skin, which is not conducive to long-term measurement. On the other hand, in conventional electrodes, electrical interference introduced by the wire leads to undesired noise problems, especially when the physiological acquisition signal is small. [0003] In response to the above problems, the design concept of the active electrode was proposed in 1968. Although this design is more useful, the...

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Problems solved by technology

Based on this, the current design of active electrodes is mainly divided into three types: one is the unit gain amplifier buffer, this design can provide high input impedance, low output impedance, and realize the function of impedance conversion, so that the electrode is sensitive to the electrophysiological signal. The acquisition ability is stronger, and the interference from the back pole wire connection is weaker; the second is a small gain amplifier. Compared with the first type, this design provides a certain signal amplification function, which can further enhance the anti-interference ability of the wire connection noise ; The third is a larger gain amplifier. This design has the strongest ability to resist noise interference. However, due to the large DC offset voltage of the human body's electrophysiological signals, this design is difficult to implement, and the larger gain is prone to mismatch, which will cause Reduce the common mode rejection ratio of the circuit

[0004] For active electrodes with integrated unity-gain amplified buffers, the circuit introduces additional noise and power consumption due to no signal amplification

However, due to the small gain of the amplifier, the noise of the amplifier itself will also affect the signal acquisition accuracy.

The active electrode integrated with a large gain amplifier is usually implemented in the form of capacitive feedback. This structure can better eliminate the DC offset voltage, but the input impedance is low, and the ability to accept physiological signals is weak. In addition, when achieving an extremely low high-pass cut-off frequency Due to the use of large resistors or capacitors to achieve large time constants, there is usually a problem of too slow signal response

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