Patent Publication Number: US-2018032780-A1

Title: Fingerprint detection circuit and electronic device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority and benefits of Chinese Patent Application No. 201510082139.X, filed with State Intellectual Property Office, P. R. C. on Feb. 13, 2015, the entire content of which is incorporated herein by reference. 
     FIELD 
     The present disclosure relates to a fingerprint detection technology field and, more particularly, to a fingerprint detection circuit and an electronic device. 
     BACKGROUND 
     In the related art, since a capacitive fingerprint detection circuit in a chip has advantages of small size and low power consumption, this kind of the fingerprint detection circuit is more preferred in a market of mobile phones and tablets. 
     The above capacitive fingerprint detection circuit detects fingerprint ridge information and fingerprint valley information. Since the distance between the fingerprint ridge and a sensing unit of the fingerprint detection unit is relatively close, and the distance between the fingerprint valley and the sensing unit of the fingerprint detection unit is relatively far, there is a difference between a ridge capacitance generated between the fingerprint ridge and the sensing unit and a valley capacitance generated between the fingerprint valley and the sensing unit. Once the ridge capacitance and the valley capacitance (referred to finger capacitance hereinafter) are detected, ridge characteristics and valley characteristics of the finger may be analyzed. 
     An output voltage output from the above fingerprint detection circuit has a proportional linear relationship with the finger capacitance (capacitance to be tested). A final result has a small difference between an output voltage corresponding to the finger capacitance of the ridge and an output voltage corresponding to the finger capacitance of the valley, so that it needs to amplify an output voltage corresponding to the finger capacitance by a predetermined factor for processing. However, the amplified factor can be limited by a range, if the amplified factor is too large, the output voltage may exceed the range to cause the data to overflow, if the amplified factor is too small, and the calculated difference between the output voltage corresponding to the finger capacitance of the ridge and the output voltage corresponding to the finger capacitance of the valley is too small, which is too difficult to identify, and the finger detection result cannot be optimized. 
     SUMMARY 
     Embodiments of the present disclosure seek to solve at least one of the problems existing in the related art to at least some extent. 
     The present disclosure provides a fingerprint detection circuit, and an electronic device. 
     According to embodiments of a first aspect of the present disclosure, a fingerprint detection circuit is provided. The fingerprint detection circuit is configured to apply an excitation signal to a finger so as to generate finger capacitors, the fingerprint detection circuit including: a signal amplifier having a negative input terminal connected with one of the finger capacitors, a positive input terminal connected with a voltage reference terminal, and an output terminal to output an output voltage according to a capacitance value of one of the finger capacitor; a capacitor; and a switch unit connected with the negative input terminal and the output terminal of the signal amplifier respectively, and configured to control the capacitor to be connected between the negative input terminal and the output terminal of the signal amplifier, such that the output voltage has a non-linear relationship with the capacitance value of one of the finger capacitors. 
     With the fingerprint detection circuit according to embodiments of the present disclosure, the output voltage of the signal amplifier has a non-linear relationship with the capacitance value of one of the finger capacitors, in the subsequent process, the output voltage of the signal amplifier can be amplified in a locally linear, such that the difference between the voltage corresponding to the ridge capacitor and the voltage corresponding to the valley capacitor becomes relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize, thus improving the effect of the fingerprint detection. 
     According to embodiments of a second aspect of the present disclosure, an electronic device is provided, and the electronic device includes the fingerprint detection circuit according to embodiments of the first aspect of the present disclosure. 
     With the electronic device according to embodiments of the present disclosure, the output voltage of the signal amplifier has a non-linear relationship with the capacitance value of one of the finger capacitors, in the subsequent process, the output voltage of the signal amplifier can be amplified in a locally linear, such that the difference between the voltage corresponding to the ridge capacitor and the voltage corresponding to the valley capacitor becomes relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize, thus improving the effect of the fingerprint detection. 
     The attached aspects and advantages of the present disclosure will be presented in following descriptions, and parts of which will become obviously in following descriptions, or learn by practice of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the drawings, in which: 
         FIG. 1  is a schematic diagram of a fingerprint detection circuit according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a schematic diagram illustrating a fingerprint collecting operation performed by the fingerprint detection circuit according to an exemplary embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram of a fingerprint detection circuit according to another exemplary embodiment of the present disclosure; and 
         FIG. 4  is a schematic diagram of an electronic device according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments will be described in detail herein, and examples thereof are illustrated in accompanying drawings. Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. 
     In the description of the present disclosure, it should be understood that, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with “first” and “second” may comprise one or more of this feature. In the description of the present invention, “a plurality of” means two or more, unless specified otherwise. 
     In the description of the present disclosure, it should be understood that, unless specified or limited otherwise, the terms “mounted,” “connected,” and “coupled” and variations thereof are used broadly and encompass such as mechanical or electrical mountings, connections and couplings, also can be inner mountings, connections and couplings of two components, and further can be direct and indirect mountings, connections, and couplings, which can be understood by those skilled in the art according to the detail embodiment of the present disclosure. 
     Various embodiments and examples are provided in the following description to implement different structures of the present disclosure. In order to simplify the present disclosure, certain elements and settings will be described. However, these elements and settings are only by way of example and are not intended to limit the present disclosure. In addition, reference numerals may be repeated in different examples in the present disclosure. This repeating is for the purpose of simplification and clarity and does not refer to relations between different embodiments and/or settings. Furthermore, examples of different processes and materials are provided in the present disclosure. However, it would be appreciated by those skilled in the art that other processes and/or materials may be also applied. 
     In the following, a fingerprint detection circuit, and an electronic device are described in detail with reference to drawings. 
       FIG. 1  is a schematic diagram of a fingerprint detection circuit according to an exemplary embodiment of the present disclosure. As shown in  FIG. 1 , the fingerprint detection circuit  100  includes a signal amplifier  102 , a capacitor  104 , and a switch unit  106 . 
     When collecting fingerprints (see  FIG. 2 ), the fingerprint detection circuit  100  may apply an excitation signal to a finger  500  so as to generate finger capacitors  114 . For example, the fingerprint detection circuit  100  may output the excitation signal via a signal generator  116 , and transmit the excitation signal to the finger  500  via an emission electrode (not shown). The excitation signal may be an alternating signal, such as a sine-wave signal, a square wave signal, or a triangular wave signal. The voltage magnitude of the alternating signal (referred to excitation voltage hereinafter) is Vt, and the frequency of the alternating signal is S. 
     The finger capacitors  114  are generated between a fingerprint of the finger  500  and a fingerprint sensor  502 . For example, the ridge capacitors are generated between a fingerprint ridge of the finger  500  and a fingerprint sensor  502 , and the valley capacitors are generated between a fingerprint valley of the finger  500  and the fingerprint sensor  502 . Each of the ridge capacitors and the valley capacitors can be referred to as the finger capacitor  114 , which is a capacitor to be measured. 
     For example, as shown in  FIG. 2 , the fingerprint sensor  502  includes a frame  504  and a two-dimensional detecting array  508  including a plurality of fingerprint sensing units  506 . 
     The frame  504  is arranged around the two-dimensional detecting array  508 , and provides the excitation signal (such as the alternating signal) when the fingerprint detecting is performed. For example, the frame  504  may be connected with the emission electrode for outputting the excitation signal. 
     Each fingerprint sensing unit  506  is configured to collect a single pixel of a fingerprint image. For example, each fingerprint sensing unit  506  usually has a size of about 50 um*50 um. A capacitance value of the finger capacitor  114  generated between the fingerprint sensing unit  506  and the finger  500  is a ridge characteristic or a valley characteristic of the fingerprint. Therefore, by detecting the capacitance values of a plurality of finger capacitors  114 , each of which is generated between one fingerprint sensing unit  506  and the finger  500 , the ridge and valley characteristics of the fingerprint image can be analyzed according to the plurality of finger capacitors  114 . 
     In an embodiment, as shown in  FIG. 1 , the signal amplifier  102  is corresponding to each fingerprint sensing unit  506  and outputs the output voltage corresponding to the finger capacitor  114 . The negative input terminal of the signal amplifier  102  is connected with the finger capacitor  114 , and the positive input terminal of the signal amplifier  102  is connected with a voltage reference terminal  118 . The signal amplifier  102  is configured to output the output voltage from the output terminal of the signal amplifier  102  according to a capacitance value of the finger capacitor  114 . 
     In an embodiment, the voltage reference terminal  118  is a ground terminal, that is, the positive input terminal of the signal amplifier  102  is connected with the ground terminal. 
     In an embodiment, the capacitor  104  may be an inner capacitor of the fingerprint sensor or other capacitors, and the capacitance value of the capacitor  104  is usually fixed. 
     The switch unit  106  is connected with the negative input terminal of the signal amplifier  102  and the output terminal of the signal amplifier  102  respectively, and is configured to control the capacitor  104  to be connected between the negative input terminal of the signal amplifier  102  and the output terminal of the signal amplifier  102 , such that the output voltage has a non-linear relationship with the capacitance value of the finger capacitor  114 . 
     In an embodiment, the first power supply  108  is connected with the capacitor  104  via the switch unit  106 , and the switch unit  106  is configured to control the first power supply  108  to charge the capacitor  106  or control the capacitor  106  to disconnect from the first power supply  108 . The first power supply  108  may be an inner power supply of the fingerprint detection circuit  100 , for example, a first electrode of the first power supply  108  is a negative electrode, and a second electrode of the first power supply  108  is a positive electrode. 
     Furthermore, the switch unit  106  includes a first switch S 1  and a second switch S 2 . The first switch S 1  includes a first selecting terminal A 1 , a first power terminal B 1  and a first connecting terminal C 1 , the first selecting terminal A 1  is connected with a first terminal of the capacitor  104 , the first power terminal B 1  is connected with the first electrode of the first power supply  108 , and the first connecting terminal C 1  is connected with the negative input terminal of the signal amplifier  102 . The second switch S 2  includes a second selecting terminal A 2 , a second power terminal B 2  and a second connecting terminal C 2 , the second selecting terminal A 2  is connected with a second terminal of the capacitor  104 , the second power terminal B 2  is connected with the second electrode of the first power supply  108 , and the second connecting terminal C 2  is connected with the output terminal of the signal amplifier  102 . The first selecting terminal A 1  may be connected with the first connecting terminal C 1  or the first power terminal B 1 , and the second selecting terminal A 2  may be connected with the second connecting terminal C 2  or the second power terminal B 2 . When the first selecting terminal A 1  is connected with the first connecting terminal C 1  and disconnected from the first power terminal B 1 , and the second selecting terminal A 2  is connected with the second connecting terminal C 2  and disconnected from the second power terminal B 2 , the capacitor  104  is connected between the negative input terminal of the signal amplifier  102  and the output terminal of the signal amplifier  102 , and disconnected from the first power supply  108 . When the first selecting terminal A 1  is connected with the first power terminal B 1  and disconnected from the first connecting terminal C, and the second selecting terminal A 2  is connected with the second power terminal B 2  and disconnected from the second connecting terminal C 2 , the first power supply  108  charges the capacitor  104 , such that two terminals of the capacitor  104  have the certain voltage. 
     In an embodiment, as shown in  FIG. 1 , the fingerprint detection circuit  100  further includes a sampling hold (S/H) circuit  110  and an analog-to-digital converter (ADC)  112 . The sampling hold circuit  110  is connected between the output terminal of the signal amplifier  102  and a terminal of the analog-to-digital converter  112 . The sampling hold circuit  110  is configured to amplify the output voltage from the output terminal of the signal amplifier  102  by a predetermined factor. The analog-to-digital converter  112  is configured to convert an amplified output voltage to a numerical value and save the numerical value. The fingerprint detection circuit  100  may further include a digital signal processor (not shown) for processing digital signals, and the digital signal processor is connected with the output terminal of the analog-to-digital converter  112 . The digitized voltages outputted from the signal amplifier  102  are convenient for following computation. 
     In an embodiment, the capacitance value of one of the finger capacitors is determined according to a formula of 
         Vo =( Vc−Vt*Cx/Ci ), 
     where, Vo is the output voltage, Vt is an excitation voltage of the excitation signal, Cx is the capacitance value of the finger capacitor  114 , Ci is the capacitance value of the capacitor  104 , and Vc is an voltage between the first terminal and the second terminal of the capacitor  104 . According to the above formula, the output voltage Vo of the signal amplifier  102  has the non-linear relationship with the capacitance value Cx of the finger capacitor  114 . 
     For example, when the fingerprint detection circuit  100  is initialized, the first selecting terminal A 1  is connected to the first power terminal B 1 , and the second selecting terminal A 2  is connected to the second power terminal B 2 , the second power terminal B 2  is connected to the positive terminal of the first power supply  108 , the first power terminal B 1  is connected to the negative terminal of the first power supply  108 , the first power supply  108  charges the capacitor  104 . After charging, the voltage over the capacitor  104  is Vc. In one embodiment, Vc=Vs, Vs is the voltage of the first power supply  108 . During initialization, two terminals of the finger capacitor  114  are connected to the ground, and the signal generator  116  is connected to the ground (i.e. Vt is connected to the ground). Then, the first selecting terminal A 1  is connected to the first connecting terminal C 1 , the second selecting terminal A 2  is connected to the second selecting terminal C 2 , and the capacitor  104  is connected between the negative terminal of the signal amplifier  102  and the output terminal of the signal amplifier  102 . At this time, the output voltage Vo from the output terminal of the signal amplifier  102  is equal to Vc, and the initialization is completed. 
     When the fingerprint detection circuit  100  collects the fingerprints, the signal generator  116  increases the excitation voltage Vt, and during the increasing of the excitation voltage Vt, the finger capacitor  114  is charged, where the electric quantity of charges is Q=Vt*Cx. Due to the virtual short and virtual off feature of the operational amplifier, the voltage outputted from the signal amplifier  102  will decrease, and the capacitor  104  is needed to charge with the same amount of charges, thus keeping the input terminal of the operational amplifier at the ground level. Then, the electric quantity charged to the capacitor  104  is (Vc−Vo)*Ci=Vt*Cx, and thus the voltage Vo outputted from the output terminal of the signal amplifier  102  is Vo=Vc−Vt*Cx/Ci. Then, the voltage Vo is amplified n times by the sampling hold circuit  110 , and the final detection voltage inputted to the AD converter  112  is Va=n*(Vc−Vt*Cx/Ci). 
     For example, when the finger  500  is put on the fingerprint sensor  502 , in a traditional detection, the first voltage corresponding to the ridge capacitor Vo 1 =−2V, and assuming that the second voltage corresponding to the valley capacitor is 15% less than the first voltage, the second voltage Vo 2 =−1.7V. If the input range of the AD converter  112  is 0˜−5V, then the sampling hold circuit  110  may amplify the first voltage and the second voltage by at most 2.5 times, i.e., the amplified first voltage Va 1 =−5V, the amplified second voltage Va 2 =−4.25V, and the difference Va 1 −Va 2 =−0.75V. 
     In an embodiment, when the fingerprint detection circuit  100  is used to collect fingerprint, and the initialized voltage over the capacitor  104  is assumed to be Vs=1.5V, then during detection, the first voltage Vo 1 =1.5=−2=−0.5V, and the second voltage Vo 2 =1.5−1.7=−0.2V. At this time, the sampling hold circuit  110  may amplify the first voltage and the second voltage 10 times, i.e., the amplified first voltage Va 1 =−5V, the amplified second voltage Va 2 =−2V, and the difference Va 1 −Va 2 =−3V, which is −3/−0.75=4 times greater than the above difference in the traditional detection. The second voltage is 60% less than the first voltage, which is 4 times greater than 15% in the traditional detection. Then, the difference between the amplified first voltage and the amplified second voltage is relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize. 
     Therefore, taking the first voltage as an example, it can be determined whether the first voltage Vo 1  is larger than or equal to −0.5V (the predetermined value), if yes, the first voltage is used to generate the fingerprint image. If no, the fingerprint detection circuit  100  can adjust at least one of the excitation voltage Vt and the voltage Vc between the capacitor  104  so as to adjust the output voltage Vo. The predetermined value setting can be considered the factors such as the range of the AD converter  112 , the security range of the excitation voltage Vt and the voltage Vc between the capacitor  104 . 
     With the fingerprint detection circuit  100  according to embodiments of the present disclosure, the output voltage of the signal amplifier  102  has a non-linear relationship with the capacitance value of one of the finger capacitors  114 . In the subsequent process, the output voltage of the signal amplifier  102  can be amplified in a locally linear form, such that the difference between the voltage corresponding to the ridge capacitor and the voltage corresponding to the valley capacitor becomes relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize, thus improving the effect of the fingerprint detection. 
       FIG. 3  is a schematic diagram of a fingerprint detection circuit according to another exemplary embodiment of the present disclosure. As shown in  FIG. 3 , the fingerprint detection circuit  100  includes a signal amplifier  202 , a capacitor  204 , a switch unit  206 , a second power supply (not shown in  FIG. 3 ), a sampling hold circuit  210  and an analog-to-digital converter  212 . 
     When collecting fingerprints (see  FIG. 2 ), the fingerprint detection circuit  200  may apply an excitation signal to a finger  500  by the fingerprint sensor  502  so as to generate finger capacitors  214 . 
     The negative input terminal of the signal amplifier  202  is connected with one of the finger capacitors  214 , the positive input terminal of the signal amplifier  202  is connected with the reference voltage terminal  216 , the signal amplifier  202  outputs the output voltage from the output terminal of the signal amplifier  202  according to the capacitance of one of the finger capacitors  214 . 
     In an embodiment, the reference voltage terminal  216  is the output terminal of the second power supply, that is, the positive terminal of the signal amplifier  202  is connected with the second power supply. 
     In an embodiment, the capacitor  204  may be an inner capacitor of the fingerprint sensor or other capacitors, and the capacitance value of the capacitor  204  is usually fixed. 
     The switch unit  206  is connected with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively, and is configured to control the capacitor  204  to be connected between the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202 , such that the output voltage has a non-linear relationship with the capacitance value of one of the finger capacitors  214 . 
     In an embodiment, the switch unit  206  is connected with the capacitor  204  in parallel. When the switch unit  206  is turned off, the capacitor  204  is communicated with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively. That is, when the switch unit  206  is turned off, the capacitor  204  is in communication with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively. When the switch unit  206  is turned on, the capacitor  204  is disconnected between the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202 . The communication means connection and turn on. In this embodiment, the switch unit  206  is turned on, although the capacitor  204  is connected between the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202 , the capacitor  204  is shorted, the capacitor  204  cannot be communicated with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively. 
     In an embodiment, the switch unit  206  includes a first connecting terminal D and a second connecting terminal D 2 . The first connecting terminal D 1  is connected between a first terminal of the capacitor  204  and the negative terminal of the signal amplifier  202 . The second connecting terminal D 2  is connected between a second terminal of the capacitor  204  and the output terminal of the signal amplifier  202 . When the switch unit  206  is turned off, the capacitor  204  is communicated with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively. That is, the first connecting terminal D 1  is disconnected from the second connecting terminal D 2 . When the switch unit  206  is turned off, the capacitor  204  is communicated with the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202  respectively. That is, the first connecting terminal D 1  is disconnected from the second connecting terminal D 2 . When the switch unit  206  is turned on, the capacitor  204  is disconnected between the negative input terminal of the signal amplifier  202  and the output terminal of the signal amplifier  202 . That is, the first connecting terminal D 1  is connected with the second connecting terminal D 2 , such that the output voltage from the output terminal of the signal amplifier  202  is equal to the voltage of the second power supply. The capacitor  204  is shorted and disconnected between the negative terminal and the output terminal of the signal amplifier  202 , which has no effect to the output voltage from the output terminal of the signal amplifier  202 . 
     In an embodiment, as shown in  FIG. 3 , the fingerprint detection circuit  200  further includes a sampling hold circuit  210  and an analog-to-digital converter  212 . The sampling hold circuit  210  is connected between the output terminal of the signal amplifier  202  and a terminal of the analog-to-digital converter  212 . The sampling hold circuit  210  is configured to amplify the output voltage from the output terminal of the signal amplifier  202  by a predetermined factor. The analog-to-digital converter  212  is configured to convert an amplified output voltage to a numerical value and save the numerical value. The fingerprint detection circuit  200  may further include a digital signal processor (not shown) for processing digital signals, and the digital signal processor is connected with the output terminal of analog-to-digital converter  212 . The digitized voltages outputted from the signal amplifier  202  are convenient for following computation. 
     In an embodiment, the capacitance value of one of the finger capacitors is determined according to a formula of 
         Vo =( Vs−Vt*Cx/Ci ), 
     where, Vo is the output voltage, Vt is an excitation voltage of the excitation signal, Cx is the capacitance value of the one of the finger capacitors  214 , Ci is the capacitance value of the capacitor  204 , and Vs is the voltage of the second power supply. According to the above formula, the output voltage Vo of the signal amplifier  202  has the non-linear relationship with the capacitance value Cx of one of the finger capacitors  214 . 
     For example, when the fingerprint detection circuit  200  is initialized, the switch unit  206  is turned on, and two terminals of the finger capacitor  214  are connected to the ground during initialization. At this time, the output voltage Vo from the output terminal of the signal amplifier  102  is equal to Vs, and the initialization is completed. 
     When the fingerprint detection circuit  200  collects the fingerprints, the switch unit  206  is turned off, and the signal generator  218  increases the excitation voltage Vt, and during the increasing of the excitation voltage Vt, the finger capacitor  214  is charged, where the electric quantity of charges is Q=Vt*Cx. Due to the virtual short and virtual off feature of the operational amplifier, the voltage outputted from the signal amplifier  202  will decrease, and the capacitor  204  is needed to charge with the same amount of charges, thus keeping the input terminal of the operational amplifier at the ground level. Then, the electric quantity charged to the capacitor  204  is (Vs−Vo)*Ci=Vt*Cx, and thus the voltage Vo outputted from the output terminal of the signal amplifier  202  is Vo=Vs−Vt*Cx/Ci. Then, the voltage Vo is amplified n times by the sampling hold circuit  210 , and the final detection voltage inputted to the AD converter  212  is Va=n*(Vc−Vt*Cx/Ci). Therefore, the output voltage Vo of the signal amplifier  202  is adjusting according to adjusting at least one of the excitation voltage Vt and the voltage of the capacitor  204 . 
     With the fingerprint detection circuit  200  according to embodiments of the present disclosure, the output voltage of the signal amplifier  202  has a non-linear relationship with the capacitance value of one of the finger capacitor  214 , in the subsequent process, the output voltage of the signal amplifier  202  can be amplified in a locally linear form, such that the difference between the voltage corresponding to the ridge capacitor and the voltage corresponding to the valley capacitor is relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize, thus improving the effect of the fingerprint detection. 
       FIG. 4  is a schematic diagram of an electronic device according to an exemplary embodiment of the present disclosure. As shown in  FIG. 4 , the electronic device  300  includes a fingerprint detection circuit. The fingerprint detection circuit may be configured inside the electronic device  300 . The fingerprint detection circuit may be any one of the above fingerprint detection circuits in the above embodiments. 
     With the electronic device according to embodiments of the present disclosure, the output voltage of the signal amplifier has a non-linear relationship with the capacitance value of one of the finger capacitor, in the subsequent process, the output voltage of the signal amplifier can be amplified in a locally linear, such that the difference between the voltage corresponding to the ridge capacitor and the voltage corresponding to the valley capacitor becomes relatively large, and the signal to noise ratio is higher, which is easier for subsequent algorithms to recognize, thus improving the effect of the fingerprint detection. 
     In an embodiment, the electronic device  300  may be a mobile phone. It can be understood that, in other embodiments, the electronic device  300  may also be a tablet PC, a notebook computer, an intelligent wearable device, an audio player, a video player, or any other electronic device having a fingerprint detection requirement. 
     A collecting window  302  of the fingerprint sensor  502  may be deposed on a front panel  304  of the electronic device  300 , and thus it is easy for collecting the fingerprints of the users. The collecting window  302  may be at other locations of the electronic device  300 , such as at a side surface or at a back surface of the electronic device  300 . 
     Thus, the electronic device  300  may have an improved fingerprint detection effect. 
     Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”. “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. 
     It should be understood that each part of the present disclosure may be realized by the hardware, software, firmware or their combination. In the above embodiments, a plurality of steps or methods may be realized by the software or firmware stored in the memory and executed by the appropriate instruction execution system. For example, if it is realized by the hardware, likewise in another embodiment, the steps or methods may be realized by one or a combination of the following techniques known in the art: a discrete logic circuit having a logic gate circuit for realizing a logic function of a data signal, an application-specific integrated circuit having an appropriate combination logic gate circuit, a programmable gate array (PGA), a field programmable gate array (FPGA), etc. 
     Those skilled in the art shall understand that all or parts of the steps in the above exemplifying method of the present disclosure may be achieved by commanding the related hardware with programs. The programs may be stored in a computer readable storage medium, and the programs comprise one or a combination of the steps in the method embodiments of the present disclosure when run on a computer. 
     In addition, each function cell of the embodiments of the present disclosure may be integrated in a processing module, or these cells may be separate physical existence, or two or more cells are integrated in a processing module. The integrated module may be realized in a form of hardware or in a form of software function modules. When the integrated module is realized in a form of software function module and is sold or used as a standalone product, the integrated module may be stored in a computer readable storage medium. 
     The storage medium mentioned above may be read-only memories, magnetic disks, CD, etc. It should be noted that, although the present disclosure has been described with reference to the embodiments, it will be appreciated by those skilled in the art that the disclosure includes other examples that occur to those skilled in the art to execute the disclosure. Therefore, the present disclosure is not limited to the embodiments.