Analog front-end circuit of bioelectric sensor

Abstract

The invention provides an analog front-end circuit of a bioelectric sensor, which comprises two feed-forward amplifiers, feedback networks of the two feed-forward amplifiers, an output common-mode voltage detector, an error amplifier, a leakage current compensator and a resistance voltage divider, and can effectively suppress common-mode components of various leakage currents.

Description

technical field [0001] The invention relates to the field of integrated circuits, in particular to an analog front-end circuit of a bioelectric sensor. Background technique [0002] The instrumentation amplifier is a precision differential voltage amplifier, which can provide high common-mode rejection ability and avoid the interference of large industrial power frequency (50Hz / 60Hz power frequency) in the environment; this interference is superimposed on the small DUT On the differential signal, the common mode part of the overall input signal is formed, usually reaching several Vpp, or even tens of Vpp. The instrumentation amplifier also provides matched high input impedance to avoid the problem that the differential signal cannot be truly extracted due to the load voltage division effect on the input signal source. In addition, the high input impedance can also reduce the common mode caused by the impedance mismatch of the differential signal source. Inhibition ability d...

AI Technical Summary

Problems solved by technology

However, this method has some limitations: First, the input common-mode voltage is locked at half of the supply voltage, which reduces the degree of design freedom and increases the difficulty of designing low-supply voltage circuits

Second, the process needs to provide a P well, which makes the method more complicated and not suitable for the common single N well process

Third, the gate leakage current from the input differential pair of the feed-forward amplifier cannot be effectively compensated

Fourth, under different process, voltage and temperature conditions, it is difficult to spontaneously compensate the leakage current according to the environmental conditions

As shown in Figure 9, as the leakage current changes from zero Initially increasing to 100fA, the differential output voltage also increases linearly to 775mV, that is, the leakage current of the input tube of the feedforward amplifier all flows through the 1TΩ large resistor connected across, so this scheme does not have any effect of compensating the leakage current

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