Abstract: In one embodiment, a controller includes a processor and a memory, the memory storing logic. The logic is configured to perform, when executed by the processor, operations including detecting, in response to driving a plurality of electrodes of a touch sensor with a first drive signal having a first polarity, a first sense signal. The first sense signal has a second polarity, the second polarity being an inverse of the first polarity. The logic is further configured to perform operations including driving, in response to detecting the first sense signal, the plurality of electrodes with a second drive signal having the second polarity.

Abstract: Embodiments herein describe an input device that includes a rectangular array of sensor electrodes connected to sensor modules that measure capacitive sensing signals corresponding to the electrodes. When performing code division multiplexing (CDM), multiple sensor electrodes are coupled to the same sensor module. As such, the sensor module generates a measurement that represents the sum of the charges on the sensor electrodes rather than an individual charge on a single sensor electrode. By repeatedly sensing multiple sensor electrodes in parallel, the input device can determine a change of capacitance for each individual sensor electrode.

Abstract: Systems, devices, and methods for fluid management in an endoscopic procedure are disclosed. In one embodiment, a fluid management device may comprise a pair of electrodes and a controller connected to the pair of electrodes. In at least some embodiments, the controller may be configured to receive signals from the pair of electrodes and determine whether a fluid in a fluid reservoir is an ionic fluid or a non-ionic fluid based on signals received from the pair of electrodes. In at least some additional embodiments, the controller may be further configured to automatically set a fluid deficit alarm threshold based on the determination of whether the fluid in the fluid reservoir is an ionic fluid or a non-ionic fluid.

Abstract: Techniques for multi-phase self-capacitance (MPSC) scanning of a sensor array are described herein. In an example embodiment, a device comprises a sensor logic coupled to a processing logic. The sensor logic is configured to concurrently sense multiple sensor elements of the sensor array in each of multiple scanning operations in order to obtain multiple measurements, where each measurement represents a collective charge of the multiple sensor elements accumulated during a corresponding scanning operation. The processing logic is configured to determine data values based on the obtained multiple measurements, where the data values respectively represent self-capacitances of the multiple sensor elements.

Abstract: A printer includes a processor; a thermal head driver circuit that drives a thermal head for printing on a printing medium; a motor driver circuit that drives a motor configured to convey the printing medium; and a power supply circuit that includes a capacitor and a first switching circuit to charge the capacitor, the power supply circuit supplying electrical power to the thermal head driver circuit and the motor driver circuit via the capacitor, wherein the processor, when stopping operation of the printer, performs a control process of discharging the capacitor via the motor driver circuit and the motor.

Abstract: A capacitor type humidity sensor is provided, where a reference capacitor (CR) is provided as an MIM (metal insulator metal) capacitor or a PIP (polysilicon insulator polysilicon) capacitor. The MIM capacitor or PIP capacitor is aligned in array structure to enable the trimming. The capacitor type humidity sensor includes a sensing capacitor (CS) connected between negative (?) drive voltage terminal (?VDRV) and an inverting terminal (?) of an operational amplifier, and a reference capacitor (CR) connected between positive (+) drive voltage terminal (+VDRV) and an output node (a) of the sensing capacitor (CS), wherein the sensing capacitor (CS) is configured to trim the reference capacitor (CR).

Abstract: An electronic device includes a touch screen controller. The touch screen controller is configured to asynchronously measure a capacitance between a sense line and a drive line of a sensing layer with respect to a horizontal sync signal of a display layer. In addition, the touch screen controller is also configured to disconnect from the sense line for a given period of time following a rising edge of the horizontal sync signal so as to reduce capacitive coupling of display noise from the horizontal sync signal to the sensing layer.

Abstract: A semiconductor device containing a terminal, a power supply voltage dropping circuit that generates a constant voltage, a switch circuit to periodically apply a constant voltage to a terminal in response to a first clock, a current-controlled oscillator circuit, and a counter, and in which the power supply voltage dropping circuit supplies a first current to the switch circuit, the current-controlled oscillator circuit generates a second clock whose frequency changes in response to the value of the first current, and the counter counts the number of second clocks within the counting time.

Abstract: Devices and methods for improving voltage handling and/or bi-directionality of stacks of elements when connected between terminals are described. Such devices and method include use of symmetrical compensation capacitances, symmetrical series capacitors, or symmetrical sizing of the elements of the stack.

Abstract: Certain aspects of the present disclosure provide apparatus and techniques for analog-to-digital conversion using a time-to-digital converter (TDC). For example, certain aspects provide a quantizer using a TDC. The quantizer may include at least one first capacitive element and a set of switches configured to selectively couple a first terminal and a second terminal of the at least one first capacitive element to at least one input voltage source. The TDC may also include a reference voltage source, at least one switch coupled between the second terminal of the at least one first capacitive element and an output of the reference voltage source, a current source selectively coupled to the first terminal of the at least one first capacitive element, and a voltage sense circuit coupled to the first terminal of the at least one first capacitive element.

Abstract: A capacitive sensor includes a switching capacitor circuit, a comparator, and a charge dissipation circuit. The switching capacitor circuit reciprocally couples a sensing capacitor in series with a modulation capacitor during a first switching phase and discharges the sensing capacitor during a second switching phase. The comparator is coupled to compare a voltage potential on the modulation capacitor to a reference and to generate a modulation signal in response. The charge dissipation circuit is coupled to the modulation capacitor to selectively discharge the modulation capacitor in response to the modulation signal.

Abstract: In one embodiment, a method includes substantially simultaneously applying a pre-determined voltage to a sense electrode and a corresponding drive electrode of a touch sensor. The application of the pre-determined voltage providing a measurement current at a capacitance including the sense electrode. The method also includes determining a difference between the measurement current at the capacitance and a reference value; and determining whether a proximity input to the touch sensor has occurred based at least in part on the difference.

Abstract: In one aspect, a fingerprint sensor device includes a substrate and a sensor chip disposed over the substrate. The sensor chip includes an array of sensor pixels configured to generate fingerprint data by sensing ridges and valleys of a surface of a finger contacting the fingerprint sensor device. Each sensor pixel includes a single sensor electrode an amplifier having an inverting terminal electrically connected to the sensor electrode and a non-inverting terminal electrically connected to a drive signal. The drive signal generates electric fields between the sensor electrode and at least one of the ridges and valleys of the surface of the finger contacting the fingerprint sensor device to generate a variable capacitor having a variable capacitance based at least partly on a distance between the sensor electrode and the at least one of the ridges and valleys of the finger.

Abstract: Disclosed are methods for measuring capacitance in presence of leakage in integrated circuits. In particular, it teaches a method of measuring leaky capacitors using charge based capacitance measurement (CBCM) technique taking into account parasitic resistance. Fast and accurate measurement of capacitances allows the estimation of a number of technology parameters like: gate-dielectric thickness, gate critical dimension, trench depth in a damascene metallization process, height of a fin in a Fin FET device etc.

Abstract: An apparatus and a method for generating signals for ESD stress testing an electronic device are disclosed. In an embodiment the apparatus is configured to receive a source signal including a source pulse, delay the source pulse to generate a test signal including a test pulse with a pulse width in an ESD time range and generate an auxiliary signal including an auxiliary pulse with a pulse width in the ESD time range.

Abstract: In one embodiment, a controller includes a processor and a memory, the memory storing logic. The logic is configured to perform, when executed by the processor, operations comprising detecting, in response to driving electrodes of a touch sensor with a first drive signal having a first polarity, a presence of a stylus. The presence of the stylus is detected based on a first sense signal, the first sense signal having a second polarity. The operations further comprise detecting, in response to driving the electrodes with a second drive signal having the first polarity, a second sense signal having a third polarity. The third polarity is an inverse of the second polarity. The operations further comprise driving, in response to detecting the second sense signal having the third polarity, the electrodes with a third drive signal having a fourth polarity. The fourth polarity is an inverse of the first polarity.

Abstract: A capacitive sensing system includes a controller, a node connected to one side of a capacitance, the controller configured to measure the capacitance by measuring a time for a voltage across the capacitance to reach a predetermined reference voltage, and the controller causing the time period for capacitance measurements to vary even when the capacitance is constant.

Abstract: An apparatus comprises a comparator that includes a first input, a second input and an output. The comparator is configured for measuring a difference in voltage between a source coupled to the first input and another source coupled to the second input, and providing information associated with the measured difference at the output. The apparatus also comprises a controllable current source coupled to the first input of the comparator and configured for supplying or drawing current. The apparatus also comprises a digital logic circuit that is configured for controlling an amount of current supplied or drawn by the controllable current source. The apparatus is configured for measuring a charge associated with an external source that is coupled to the first input of the comparator.

Abstract: Provided are a touch sensing apparatus and a method of driving the same. The touch sensing apparatus includes a signal source configured to output a driving signal, a touch panel configured to be driven by the driving signal output by the signal source and output a current signal generated using the driving signal, a charge amplifier configured to convert the current signal output by the touch panel into a voltage signal, and a controller configured to control the charge amplifier to be periodically reset.

Abstract: A device for measuring a variation (?CX) of a capacitance (CX), includes: elements for charging the capacitance (CX) on the basis of a supply voltage (VCC). elements for discharging the capacitance (CX) into a reference capacitance (CS) in a fixed number of discharges (x), elements for measuring a voltage (VS) and for detecting a threshold of voltage (VTH) across the terminals of the reference capacitance (CS). elements for charging with current (IC) the reference capacitance (CS) on the basis of the supply voltage (VCC) for a duration (t), after the transfer of charge from the capacitance (CX) into the reference capacitance (CS), and elements for measuring the variation between the duration (t) with respect to a previously measured duration so as to estimate the variation (?CX) of the capacitance (CX).

Abstract: A processing system for an input device includes a sensor module coupled to first sensor electrodes and second sensor electrodes. The sensor module includes sensor circuitry and is configured to acquire mutual capacitive measurements between the first sensor electrodes and the second sensor electrodes, and acquire absolute capacitive measurements of the first sensor electrodes and the second sensor electrodes. The processing system further includes a determination module configured to determine a projection from the mutual capacitive measurements and a profile from the absolute capacitive measurements, and determine a low ground mass correction factor based on a good ground value, the projection, and the profile.

Abstract: A capacitance measurement device for measuring the capacitance of a measured capacitor includes a charging control unit for charging the measured capacitor; a discharging control unit for discharging the measured capacitor; a voltage converting circuit coupled to the measured capacitor, for converting a voltage signal on the measured capacitor into a value that represents the capacitance of the measured capacitor; wherein in a first period, one of the charging control unit and the discharge control unit charges/discharges the measured capacitor and in a second period after the first period, the other one of the charging control unit and the discharge control unit discharges/charges the measured capacitor.

Abstract: A circuit breaking arrangement is adapted to be connected to a current path in at least one transmission line arranged to carry an electrical current for controllably effecting discontinuation of flow of electrical current in the at least one transmission line. The circuit breaking arrangement includes a plurality of series connections of a plurality of power semiconductor switching elements. The plurality of series connections of power semiconductor switching elements are connected in parallel relatively to each other.

Abstract: A system for determining a conductance of an object includes a sensor configured to emit an electromagnetic field when an excitation signal is received, wherein the electromagnetic field interacts with the object when the object is positioned within the electromagnetic field. A signal processing circuit is coupled to the sensor and configured to provide an adjustable capacitance to the sensor to adjust a phase angle of a current flowing through the sensor, to generate a voltage measurement representative of a voltage across the sensor, and to generate a current measurement representative of the current flowing through the sensor. A controller is coupled to the signal processing circuit and configured to calculate an admittance of the sensor based on the voltage measurement and the current measurement, and to determine a conductance of the object based on the calculated admittance of the sensor.

Abstract: An approach for transmission line pulse and very fast transmission line pulse reflection control is provided. The approach includes using a power splitter to split an incident pulse into two identical pulses with one going to a device under test (DUT) through a delivery cable and the other going down an open ended delay cable. The structure of the power splitter, along with having the delivery cable and the open ended delay cable with the same signal propagation time and pulse transmission characteristics enable the canceling of pulse reflections from the DUT.

Abstract: A capacitive sensing device can include multiple capacitive sensors. A first device controller is operatively connected to a portion of the capacitive sensors, while a second device controller is operatively connected to another portion of capacitive sensors. A common node or shield can be connected between the first device controller and the second device controller. Charging and discharging events of selected drive lines in the capacitive sensing device and/or of the common node or shield can be synchronized to reduce undesirable effects such as noise and/or to prevent the charging events and the discharging events from overlapping with each other. One or more reference capacitive sensors can be shared by the multiple device controllers.

Abstract: The present disclosure is directed to a method and apparatus for estimating ambient light conditions for an OLED display. Embodiments of the method and apparatus use one or more columns of OLEDs in the display to perform two functions: their typical function of emitting light in a display mode, and the additional function of sensing light in a sense mode. To perform the additional sense mode functionality, the one or more columns of OLEDs in the display are temporarily placed into a photovoltaic and/or photoconductive mode. A sensing circuit is used to measure this current produced by the one or more columns of OLEDs while operating in the sense mode and report it back to a controller. The controller can then use this information to estimate the ambient light conditions of the environment where the OLED display is currently operating and to perform a touch and/or proximity sensing function.

Abstract: In one embodiment, a touch-sensitive device includes a controller, horizontal electrodes, and vertical electrodes. The touch-sensitive device further includes a first plurality of switches that couple the horizontal electrodes to a first plurality of sensors, a second plurality of switches that couple the vertical electrodes to a second plurality of sensors, and a third and fourth plurality of switches that couple the horizontal and vertical electrodes to a shield sensor. The controller is operable to perform simultaneous hovering, touch, and proximity detection by selectively controlling the first, second, third, and fourth plurality of switches. The hovering, touch, and proximity detection includes causing substantially equal voltages to be present on the horizontal and vertical electrodes while measuring capacitances using the shield sensor and either the first or second plurality of sensors.

Abstract: An input device comprises a first and second pluralities of capacitive sensor electrodes. The first plurality of capacitive sensor electrodes is oriented along a first axis, disposed in a first layer, and configured to update a display screen of the input device. The second plurality of capacitive sensor electrodes is oriented along a second axis that differs from the first axis. A display region of the display screen has a first dimension along the first axis and a second dimension the second axis. At least one sensor electrode of the first plurality of capacitive sensor electrodes extends fully across the first dimension of the display region. Individual sensor electrodes of the second plurality of capacitive sensor electrodes do not extend fully across the second dimension of the display region.

Abstract: A capacitive sensor device includes a sensor electrode coupled to a first switch and coupleable either to a sensor operating voltage or to an evaluation circuit, configured as a power source circuit. A first current path is coupleable to the sensor electrode at an input end and to ground via a collector and emitter of a first transistor by an auxiliary resistor. A second current path is coupled to a reference potential at one end. A capacitor is coupled between the reference potential and a second transistor. A second auxiliary resistor is arranged in the second current path. The first transistor's base and collector are coupled to the base of the second transistor. A compensation capacitor has a first terminal coupled to the first current path and a second terminal couplable to a compensation voltage, to ground, or in a floating manner via a second switch.

Abstract: A capacitance detecting method disclosed herein, which achieves a good detection accuracy, a good resolution, and a high-speed operation, (A) (a) drives, on the basis of code sequences (di (=di1, di2, . . . , diN, where i=1, . . . , M)) which are orthogonal to one another and include ±1 and each of which has a length N, drive lines (DL1 through DLM) in parallel for each of (I) a first capacitance column (Ci1) between the drive lines and a first sense line (SL1) and (II) a second capacitance column (Ci2) between the drive lines and a second sense line (SL2) so that voltages ±V are applied and (b) outputs outputs (sFirst=(s11, s12, . . . , s1N)) from the first capacitance column (Ci1) and outputs (sSecond=(s21, s22, . . .

Abstract: A capacitance sense system can include a capacitance sense input configured to receive an input signal that varies according to a sensed capacitance; an integrator/discharge circuit configured to integrate the input signal and discharge the integrated input signal toward the reference level in conversion operations; and a remainder retainer section configured to quantize the discharging of the integrated input signal, and retain any remainder of the integrated input signal that follows a quantization point for a next conversion by the integrator/discharge circuit.

Abstract: In certain embodiments, an apparatus comprises a charge-measurement capacitor and circuitry. The circuitry is configured to provide a pre-determined amount of charge to the charge-measurement capacitor and transfer an accumulated amount of charge on a sense electrode to the charge-measurement capacitor, the accumulated amount of charge having accumulated on the sense electrode due at least in part to noise. The circuitry is configured measure a voltage of the charge-measurement capacitor to determine the accumulated amount of charge.

Abstract: A capacitive proximity sensor has a first sensor electrode and a second sensor electrode, a signal generator for providing a first and a second electric alternating signal, a first load element which comprises a first and a second electric load, in which the first alternating signal by the first load can be fed to the first sensor electrode and the second alternating signal by the second load to the second sensor electrode, and wherein the electric loads each together with the capacitive load to be measured at the respective sensor electrode form a lowpass filter, and a signal processing device, which is coupled with the first sensor electrode and with the second sensor electrode, and which is adapted to form a first measurement value from the push-pull portion of a first electric parameter tapped at the first sensor electrode and a second electric parameter tapped at the second sensor electrode.

Abstract: There are provided a touchscreen device and a method of driving the same. The touchscreen device includes: a panel unit including a plurality of first electrodes extending in a first direction and a plurality of second electrodes extending in a second direction; and a control unit applying predetermined driving signals to at least one first electrode among first electrodes arranged sequentially from a first thereof and to at least one first electrode among first electrodes arranged sequentially from a last thereof, and detecting a change in capacitance from at least one of the first electrodes among electrodes disposed in a central portion, to thereby determine a touch.

Abstract: A capacitance detection device of a capacitance system includes: a capacitance sensor electrode for detecting a capacitance; a power source for supplying charges to be charged in the capacitance sensor electrode; an electric charge storage capacitor in which an amount of charges to be charged therein changes according to the electric charges charged in the capacitance sensor electrode; and a switch for changing a reference potential of the electric charge storage capacitor. The reference potential of the electric charge storage capacitor is changed in a period of measuring the capacitance.

Abstract: Apparatus and methods of de-convolution for multi-phase scans of an array of electrodes are described. One programmable circuit includes a sequencer to initiate a multi-phase transmit (TX) scan of an array of electrodes to obtain capacitance data. The capacitance data is stored in one or more storage devices as convoluted capacitance data. The programmable circuit also includes a digital circuit block to read the convoluted capacitance data from the one or more storage devices, de-convolve the convoluted capacitance data to obtain de-convoluted capacitance data, and store the de-convoluted capacitance data in the one or more storage devices.

Abstract: A system for measuring capacitance has a measurement circuit with a first reference capacitor connected to a first node and to a second node. Each of the nodes is connected to a unit operable to apply a reference voltage or ground to one of the nodes. Each node has a first pad connected to the first node and a unit operable to measure voltage between the first node and second node.

Abstract: A method for evaluating a capacitance of a sensor electrode of a proximity sensor includes charging the electrode with a charge voltage. Simultaneously, a compensation capacitance is charged by coupling the compensation capacitance between a reference voltage and ground. The sensor electrode and the compensation capacitance are decoupled from voltage sources and a state of charge of the sensor electrode and of the compensation capacitance is maintained. The sensor electrode is coupled to the compensation capacitance and the charges are balanced; then decoupled from the compensation capacitance and the charge is maintained. The compensation capacitance is then coupled to an evaluation network. The charge of a hold capacitance in the evaluation network is reversed by a charge-reversal current which is dependent on the current flow of the compensation capacitance. The charge of the hold capacitance is evaluated after one or more such cycles.

Abstract: A read out circuit for a sensor uses a feedback loop to bias the sensor to a desired operating point, such as the maximal possible sensitivity, but without the problem of an instable sensor position as known for the conventional read-out with constant charge. The reference bias to which the circuit is controlled is also varied using feedback control, but with a slower response than the main bias control feedback loop.

Abstract: An integratable capacitive touch sensing circuit through charge sharing is provided, including a charge sharing circuit, voltage-controlled oscillator, reference frequency generator, switch clock generator and frequency compare circuit; wherein charge sharing circuit further including a sensing capacitor, touch capacitor, share capacitor, charging switch, charge sharing switch and discharging switch, for sharing charge from charged sensing capacitor with discharged share capacitor through charge sharing to accumulate voltage on share capacitor. The capacitance of share capacitor is adjustable for applications generating different sensing capacitance. The charging switch, charge sharing switch and discharging switch are controlled by non-overlapping clocks. Prolonging close duration of charging switch and minimizing close duration of charge sharing switch and discharging switch can minimize interference from ambient noise.

Abstract: Method of searching for a variation in capacitance of a capacitive sensor, includes a phase of searching for variation in capacitance and, when a capacitance variation has been detected, a phase of verifying the variation in capacitance. The search phase includes a recurrent step of searching for variation in capacitance including steps of measuring the duration of a first measurement sequence and determining, according to the measured duration, whether a first predefined detection criterion for variation in capacitance is verified. The verification phase includes steps of measuring the duration of a second measurement sequence and determining, according to the measured duration, whether a second predefined detection criterion for variation in capacitance is verified.

Abstract: A circuit for sensing a differential capacitance includes a charge-storing circuit to generate a first output voltage and a second output voltage related to capacitances at two terminals of the differential capacitance, respectively, an operational amplifier to amplify the difference between the first and second output voltages to generate a sensing value, a first sampling capacitor having one terminal connected to the negative input terminal and the other terminal receiving the first or second output voltage, and a second sampling capacitor having one terminal connected to the negative input terminal and the other terminal switched to the output terminal of the operational amplifier. The second sampling capacitor stores a non-ideal error value to offset the non-ideal effect of the operational amplifier imparted on the sensing value.

Abstract: In one embodiment, a method includes discharging a first capacitor and discharging a set of capacitances present on a first set of lines of a touch sensor. After discharging the first capacitor and the set of capacitances, the method further includes causing charge to be transferred to the set of capacitances during a first time period. After the first time period, the method includes causing charge to be transferred to the first capacitor and the set of capacitances during a second time period. After the second time period, the voltage across the first capacitor to a first threshold is compared. The method also includes determining whether a touch was detected by the touch sensor based on comparing the voltage across the first capacitor to the first threshold.

Abstract: A detection circuit is provided with a differential capacitive sensor and with an interface circuit having a first sense input and a second sense input, electrically connected to the differential capacitive sensor. Provided in the interface circuit are: a sense amplifier connected at input to the first sense input and to the second sense input and supplying an output signal related to a capacitive unbalancing of the differential capacitive sensor; and a common-mode control circuit, connected to the first sense input and to the second sense input and configured to control a common-mode electrical quantity present on the first sense input and on the second sense input. The common-mode control circuit is of a totally passive type and is provided with a capacitive circuit, which is substantially identical to an equivalent electrical circuit of the differential capacitive sensor and is driven with a driving signal in phase opposition with respect to a read signal supplied to the differential capacitive sensor.

Abstract: An apparatus comprises a comparator that includes a first input, a second input and an output. The comparator is configured for measuring a difference in voltage between a source coupled to the first input and another source coupled to the second input, and providing information associated with the measured difference at the output. The apparatus also comprises a controllable current source coupled to the first input of the comparator and configured for supplying or drawing current. The apparatus also comprises a digital logic circuit that is configured for controlling an amount of current supplied or drawn by the controllable current source. The apparatus is configured for measuring a charge associated with an external source that is coupled to the first input of the comparator.

Abstract: A voltage measuring apparatus for use in an energy harvesting system is disclosed. The apparatus includes a capacitor (6) adapted to be charged by means of a voltage to be measured, and an asynchronous digital counter (12) having power supply terminals adapted to be selectively connected to the capacitor during discharge of the capacitor and to provide a digital output signal dependent upon the voltage level of the capacitor the start of discharging of the capacitor.

Abstract: According to one embodiment, an electronic device includes a capacitor, a power supply device, a discharger and a capacitance detector. The capacitor is used as a backup power supply. The power supply device charges the capacitor. The discharger discharges the capacitor. The capacitance detector maintains a terminal voltage of the capacitor at a given level for a predetermined time, by controlling an operating time of the power supply device. The capacitance detector allows the discharger to start the discharge the predetermined time later. The capacitance detector detects a capacitance of the capacitor based on a transient response characteristic of the discharge.

Abstract: A pad capacitance test circuit may be coupled to one or more pads of an electronic circuit, such as a processor. The pad capacitance test circuit may be located on a die including the electronic circuit. The pad capacitance test circuit may reset a pad voltage of one or more of the pads to zero, and then couple the pad to a supply voltage through a pullup resistor for a time period. The final pad voltage at or near the end of the period of time may be measured. The pad capacitance may be determined from the measured value of the final pad voltage and known values of the supply voltage, the time period, and resistance of the pullup resistor.

Abstract: A transconductance amplifier mirror circuit is connected to an electrode for sensing the capacitance of the electrode with reference to ground, or the capacitance between the electrode and another electrode. A voltage level change is produced on the electrode connected to the transconductance amplifier mirror circuit to cause the transconductance amplifier mirror circuit to supply charges to or drain charges from a charge calculation circuit. The charge amount variation is converted to a signal for calculating the sensed capacitance.