Sensor circuit

Abstract

The invention provides a sensor circuit which comprises a sensor, a preprocessing circuit and an impedance biasing circuit, wherein the sensor is connected to the preprocessing circuit through an input connection wire. The impedance biasing circuit is connected between the input connection wire and a bias point and comprises a first impedance switching circuit and a second impedance switching circuit. The first impedance switching circuit comprises a first transistor and a second transistor. The first transistor and the second transistor are connected to form a first current mirror. The second impedance switching circuit comprises a third transistor and a fourth transistor. The third transistor and the fourth transistor are connected to form a second current mirror. The second current mirror is connected to the first current mirror in a reverse matching current mirror mode and receives bias voltage supplied by the bias point. The first transistor, the second transistor, the third transistor and the fourth transistor work in a sub-threshold region under the action of the bias voltage.

Description

technical field [0001] The present invention relates to electronic circuit technology and, in particular, to a sensor circuit with self-biased high input impedance. Background technique [0002] With the development of sensing technology, capacitive sensors are widely used in consumer electronic products to implement accelerometers, gyroscopes, microphones, etc. because they can automatically detect and generate corresponding detection signals. Generally, the input terminal of the amplifier (Amplifier) ​​or buffer (Buffer) needs to be biased at the normal operating voltage. The capacitance of the capacitive sensor is generally small, about several pF. Therefore, it can be used at the input terminal of the amplifier or buffer Simply connect a high-resistance resistor, about a giga-ohm range of resistance, but because a high-resistance resistor usually takes up a large device area, the above-mentioned high input impedance implementation method is rarely used in actual circuit ...

AI Technical Summary

Problems solved by technology

For example, when the sensing voltage signal output by the sensor is large, the effective impedance of the impedance bias circuit is relatively large when the forward large signal is large, and the effective impedance is small when the reverse large signal is large; and , the impedance bias circuit using the current mirror may also cause rectification effect due to parity distortion; the impedance nonlinearity and rectification effect of the above impedance bias circuit may cause the DC operating point of the amplifier or buffer to drift

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