A fingerprint recognition sensor
A fingerprint identification and sensor technology, which is applied in character and pattern recognition, instruments, computer components, etc., can solve the problem of limited input and output ranges of fingerprint identification sensors, limited linearity of fingerprint identification circuit systems, and narrow linear range of OP structures. and other problems, to achieve the effect of improving the closed-loop input and output range, avoiding the rapid drop of gain, and avoiding the limitation of linearity
Active Publication Date: 2017-11-24
SILEAD
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When the signal voltage at the OP output terminal is relatively high, M2 will first enter the linear region (that is, enter the interval from 201 to 202 into the interval from 202 to 203), and the gain of the cascode stage formed by M2 will drop quickly. So the total gain of the OP falls off very quickly, eventually causing the OP to no longer amplify linearly
Similarly, when the signal voltage at the OP output terminal is relatively low, M3 will first enter the linear region (that is, enter the interval from 204 to 203 into the interval from 203 to 202), and the gain of the cascode stage formed by M3 will drop quickly. Going down, the final OP is no longer linearly enlarged; thus resulting in a narrow linear interval of the entire OP structure
Therefore, the input and output ranges of the fingerprint recognition sensor are limited, which in turn leads to the limitation of the linearity of the entire fingerprint recognition circuit system, which affects the compromise between the noise and linearity of the system, and finally shows that the sensitivity of the system is low.
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[0027] In order to make the object, technical solution and advantages of the present invention clearer, various embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, those of ordinary skill in the art can understand that, in each implementation manner of the present invention, many technical details are provided for readers to better understand the present application. However, even without these technical details and various changes and modifications based on the following implementation modes, the technical solution claimed in each claim of the present application can be realized.
[0028] The first embodiment of the present invention relates to a fingerprint identification sensor, such as image 3 As shown, it includes an inverter structure operational amplifier OP composed of four MOS transistors (M1, M2, M3, M4), two of which are cascode structure MOS transistors, that is, PMOS transistor M2 and NMOS...
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The invention relates to the field of fingerprint identification and discloses a fingerprint identification sensor. In the present invention, by connecting the auxiliary operational amplifier to the gate of the cascode structure MOS transistor, when the source-drain voltage of the cascode structure MOS transistor is reduced, the gain amplification effect of the auxiliary operational amplifier can be used to make the entire fingerprint identification The gain of the sensor remains high, which avoids the rapid drop in the gain of the entire fingerprint recognition sensor caused by the gain drop of the cascode structure MOS tube, thereby increasing the closed-loop input and output range, that is, improving the linearity; when fingerprint recognition When the linearity of the sensing array of the sensor is relatively high, the effective signal amplitude of the fingerprint recognition sensor can be increased, thereby reducing the influence of noise on the signal, improving the signal-to-noise ratio, and finally achieving high sensitivity.
Description
technical field [0001] The invention relates to the field of fingerprint identification, in particular to a fingerprint identification sensor. Background technique [0002] The structure diagram of the existing fingerprint identification sensor is as follows: figure 1 As shown, among them, four metal-oxide-semiconductor (MOS) tubes M1, M2, M3, and M4 constitute an inverter structure OP (Operational Amplifier, operational amplifier), and the drain of M2 is connected to the drain of M3 Together as the OP output terminal, the OP output terminal is connected to the gate of the follower M5, the M5 output terminal (drain) is connected to the drain of the switch tube M6, and the source of M6 is used as the output terminal Vo of the fingerprint recognition sensor. The end of the OP is connected to the switching tube M7, that is, the gate of M4 is the input terminal of the OP, the drain of M7 is connected to the gate of M4, and the source of M7 is connected to the output terminal of...
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IPC IPC(8): G06K9/62
Inventor 东尚清
Owner SILEAD