Pressure sensing key detection differential circuit and electronic equipment

Abstract

The invention provides a pressure sensing key signal detection circuit. The circuit comprises an integrated operational amplifier, and a pressure sensing bridge type measuring circuit; the first end of the pressure sensing bridge type measuring circuit is connected with the non-inverting input end of the integrated operational amplifier, and the second end of the pressure sensing bridge type measuring circuit is connected with the inverting input end of the integrated operational amplifier through a first capacitor; a first resistor is connected between the inverting input end and the output end of the integrated operational amplifier in parallel; and a second resistor is connected between the non-inverting input end and the inverting input end of the integrated operational amplifier in parallel. The resistor is connected between the non-inverting input end and the inverting input end of the operational amplifier in parallel, so that differential capacitors or coupling capacitors can be charged, and the starting speed and stability are improved.

Description

Technical field [0001] The invention relates to the field of detection circuits, in particular to a detection circuit and electronic equipment of a pressure-sensitive button of a mobile phone. Background technique [0002] The pressure-sensitive button signal detection circuit is essentially a strain gauge measurement circuit. The strain gauge measurement circuit has requirements for the resistance parameters of the strain gauge. The resistance values ​​of the four resistors of the bridge are required to be consistent, otherwise it will cause the bridge to be unbalanced and there is a fixed Bias voltage output. This offset voltage is called Offset. The pressure-sensitive keys are currently produced in the form of printed induction resistors. Because the accuracy of printing is difficult to control, as low-cost sensors, the offset of this type of sensor is much larger than that of MEMS and conventional strain gauge sensors, reaching 400-600mV . The detected strain signal is onl...

AI Technical Summary

Problems solved by technology

The problem is that the structure of an extra DAC is complicated and the cost increases; at the same time, the DAC will cause interference and the signal-to-noise ratio will decrease

At present, the smallest signal they can detect is greater than the noise. The noise is 20uV. If the Offset deviation is large, the noise will be 3-4 times larger.

[0004] The differential circuit ZL201620410244.1 proposed by the applicant before avoids the noise introduced by the DAC and can detect a signal of 1.5uV, but due to the slow charging process of the differential capacitor, the start-up stabilization time is very long

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