Abstract: A resonator element includes a base section, a pair of vibrating arms projecting toward the same side from the base section, and disposed side by side in a predetermined direction, a support arm projecting from the base section toward the same side as the pair of vibrating arms, disposed between the pair of vibrating arms, and having a recessed portion disposed on one principal surface, and a first electrically-conductive pad and a second electrically-conductive pad disposed side by side across the recessed portion.

Abstract: A calibrated crystal warm-up method that can include determining the number of clock cycles of a crystal clock reference signal from a crystal oscillator occur during a single clock cycle of a low-power oscillator. Further, the determination can occur when the crystal oscillator is warmed up. The method can also include comparing a number of clock cycles of the crystal clock reference signal with a previously determined number of clock cycles of the crystal clock reference signal to indicate whether the crystal oscillator is warmed up. Further, the method can include counting the number of clock cycles of a low-power clock reference signal have occurred up until the time it has been determined that the crystal oscillator has been warmed up.

Abstract: The invention relates to a controller, and more particularly, to systems, devices and methods of controlling a sensor having a resonating mass. The controller includes: an analog-to-digital converter (ADC) unit for extracting a digitized sensor signal from the sensor signal; a phase controller for generating, based on the digitized sensor signal, a phase-controlled signal that is locked in phase with the digitized sensor signal; an amplitude controller for applying a gain to the digitized sensor signal to thereby generate an amplitude-adjusted signal; a modulator for modulating the amplitude-adjusted signal to thereby generate a modulated signal; and a phase shifter for shifting the phase of the modulated signal by 90 degrees. The output signal from the phase shifter is amplified and input to the drive for exciting the resonating mass, to thereby form a closed resonance loop for controlling the oscillation amplitude of the resonating mass.

Abstract: A technique decouples a MEMS device from sources of strain by forming a MEMS structure with suspended electrodes that are mechanically anchored in a manner that reduces or eliminates transfer of strain from the substrate into the structure, or transfers strain to electrodes and body so that a transducer is strain-tolerant. The technique includes using an electrically insulating material embedded in a conductive structural material for mechanical coupling and electrical isolation.

Abstract: A technique decouples a MEMS device from sources of strain by forming a MEMS structure with suspended electrodes that are mechanically anchored in a manner that reduces or eliminates transfer of strain from the substrate into the structure, or transfers strain to electrodes and body so that a transducer is strain-tolerant. The technique includes using an electrically insulating material embedded in a conductive structural material for mechanical coupling and electrical isolation. An apparatus includes a MEMS device including a first electrode and a second electrode, and a body suspended from a substrate of the MEMS device. The body and the first electrode form a first electrostatic transducer. The body and the second electrode form a second electrostatic transducer. The apparatus includes a suspended passive element mechanically coupled to the body and electrically isolated from the body.

Abstract: An oscillator system having: an UHF oscillator, such as a SAW oscillator, for producing a signal having a controllable frequency; a passive vibration, suppressor mechanically coupled to the UHF oscillator for suppressing vibrations above a predetermined bandwidth BW1 on the UHF oscillator; and an active vibration suppressor. The active vibration suppressor includes an accelerometer for sensing vibrations within a predetermined bandwidth BW2 on the UHF oscillator; and an HF or VHF oscillator, such as a crystal oscillator, producing a signal having a frequency controlled by the accelerometer. A control loop having a bandwidth changeable with sensed vibration level is fed the oscillator and the UHF oscillator for controlling the frequency of the signal produced by the SAW oscillator in accordance with a difference between the signal produced the HF or VHF oscillator and the signal produced by the UHF oscillator, the control loop having a bandwidth BW3; where BW1<BW3<BW2.

Abstract: A digitally-controlled oscillator circuit receives a digital value and generates a driving signal for driving an oscillator at a frequency according to the received digital value. A time-to-digital converter circuit receives a detection signal of oscillation of the oscillator, receives the driving signal, and detects a phase difference between the detection signal and the driving signal. A control circuit receives the detected phase difference and controls the frequency of the driving signal generated by the digitally-controlled oscillator circuit, such that the detected phase difference coincides with a predetermined resonant phase difference to resonate the oscillator.

Abstract: A tunable resonator is provided that has a high Q for each resonate frequency. The tunable resonator is a MEMs tunable resonator wherein the tuner is affected by moving a moveable mass, associated with the resonating portion of the resonator, form a first position to a second position such that the moveable mass is held in the first position or second position by a detent rather than a constant electromagnet magnetic or electrostatic force applied thereon.

Abstract: A crystal oscillator and manufacturing method thereof are provided.

Abstract: A MEMS device and method for amplitude regulation of a MEMS device are disclosed. In a first aspect, the MEMS device comprises a MEMS resonator, a limiter coupled to the MEMS resonator, and a regulator coupled to the limiter. The MEMS device includes an amplitude control circuit coupled to the MEMS resonator. The amplitude control circuit controls a supply of the limiter via the regulator to regulate oscillation loop amplitude of the MEMS device. In a second aspect, the method includes coupling a regulator to the limiter, coupling an amplitude control circuit to the MEMS resonator, and controlling a supply of the limiter via the regulator to regulate oscillation loop amplitude of the MEMS device.

Abstract: There are disposed a sealing member, a pair of electrode pads to electrically couple a piezoelectric resonator, a plurality of connection pads to electrically couple an integrated circuit element and the piezoelectric resonator, and wiring patterns to establish electrical continuity between the pair of electrode pads and the plurality of connection pads, and the piezoelectric resonator and the integrated circuit element are disposed side by side in plan view. An output wiring pattern establishes electrical continuity between one of the connection pads and an alternating current output terminal of an oscillation circuit, and a power source wiring pattern establishs electrical continuity between one of the connection pads and a direct current power source terminal of the oscillation circuit. The electrode pads are disposed closer to the power source wiring pattern than the output wiring pattern.

Abstract: A system and method in accordance with the present invention provides a gyroscope incorporating an improved PLL technique. The improved PLL auto-corrects its own reference low-frequency noise, thereby eliminating this source of noise, improving the noise performance of the gyroscope and allowing a compact implementation. The net result is a gyroscope with improved bias stability that can meet noise requirements with a smaller footprint.

Abstract: A variable phase amplifier circuit is disclosed and its method of use in tuning devices having resonators. The variable phase amplifier receives an input differential signal pair. The input differential signal pair can be generated by a resonator device. The variable phase amplifier generates a modified differential signal pair in response to receiving the input differential signal pair. The variable phase amplifier provides a means to vary the phase of the modified differential signal pair with respect to the input differential signal pair, in an accurate and stable manner. If the modified differential signal pair with a phase shift introduced in it is fed back to the resonator device, the resonator will change its frequency of oscillation, where the new frequency of oscillation is a function of the phase of the modified differential signal pair.

Abstract: An apparatus for determining and/or monitoring at least one process variable of a medium, comprising: an oscillatable unit, which has a membrane and at least one oscillatable element, wherein the oscillatable element is secured to the membrane at least in a first securement region and in a second securement region. At least one driving/receiving unit, which excites the oscillatable unit to execute mechanical oscillations and which produces a received signal dependent on the oscillations of the oscillatable unit; and a control/evaluation unit, which evaluates the received signal with reference to the process variable. The apparatus is distinguished by features including that the driving/receiving unit is embodied in such a manner and arranged on a rear face of the membrane facing away from the oscillatable element that the oscillatable element executes torsional oscillations.

Abstract: An oscillator has an oscillation portion that generates oscillatory electric signals due to a magnetization motion; and a first electric circuit that is connected in parallel to the oscillation portion. A current whose magnitude oscillates flows to the first electric circuit, and the first electric circuit is arranged such that a magnetic field generated by the current is applied to the oscillation portion.

Abstract: A fractional-N divider supplies a divided clock signal. An adjusted divided clock signal is generated in a digital-to-time converter circuit having a delay linearly proportional to digital quantization errors of the fractional-N divider. The adjusted divided clock signal is generated based on first and second capacitors charging to a predetermined level. The charging of the first and second capacitors is interleaved in alternate periods of the divided clock. The charging of each capacitor with a current corresponding to respective digital quantization errors is interleaved with charging with a fixed current. A first edge of a first pulse of the adjusted divided clock signal is generated in response to the first capacitor charging to a predetermined voltage and a first edge of a next pulse of the adjusted divided clock signal is generated in response to the second capacitor charging to the predetermined voltage.

Abstract: The invention relates to a controller, and more particularly, to systems, devices and methods of controlling a sensor having a resonating mass. The controller includes: an analog-to-digital converter (ADC) unit for extracting a digitized sensor signal from the sensor signal; a phase controller for generating, based on the digitized sensor signal, a phase-controlled signal that is locked in phase with the digitized sensor signal; an amplitude controller for applying a gain to the digitized sensor signal to thereby generate an amplitude-adjusted signal; a modulator for modulating the amplitude-adjusted signal to thereby generate a modulated signal; and a phase shifter for shifting the phase of the modulated signal by 90 degrees. The output signal from the phase shifter is amplified and input to the drive for exciting the resonating mass, to thereby form a closed resonance loop for controlling the oscillation amplitude of the resonating mass.

Abstract: A capacitively-driven Micro-Electro-Mechanical System (MEMS) resonator is provided, in which a piezoresistively differential measurement is used to enable the MEMS resonator to transfer a signal. The MEMS resonator uses a Complementary Metal-Oxide-Semiconductor (CMOS) manufacturing process to make its oscillator and piezoresistor to achieve electrical insulation, thereby lowering the level of feedthrough signal.

Abstract: A system and method is disclosed that provides a technique for generating an accurate time base for MEMS sensors and actuators which has a vibrating MEMS structure. The accurate clock is generated from the MEMS oscillations and converted to the usable range by means of a frequency translation circuit.

Abstract: A resonance circuit includes a first resonator, a second resonator, a capacitance element and an inverting amplifier, and a negative capacitance circuit. The second resonator is connected to the first resonator in series. The capacitance element and the inverting amplifier are connected to one another in series. The capacitance element and the inverting amplifier are connected to the first resonator in parallel. The negative capacitance circuit is connected between a node and ground. The node is disposed between the first resonator and the second resonator.

Abstract: A SAW device includes a SAW chip formed of a piezoelectric substrate and an IDT formed thereon, a base substrate that supports the SAW chip, and a fixing member that fixes the SAW chip to the base substrate. The SAW chip that forms a cantilever is supported by the base substrate via the fixing member in a position where the IDT does not overlap with the fixing member in a plan view of the SAW chip. The length W of the SAW chip in a y-axis direction and the length D of the fixing member in the y-axis direction satisfy 1<D/W?1.6. The fixing member bonds the lower surface and side surfaces of the fixed end of the SAW chip to the base substrate.

Abstract: Doubly-clamped nanowire electromechanical resonators that can be used to generate parametric oscillations and feedback self-sustained oscillations. The nanowire electromechanical resonators can be made using conventional NEMS and CMOS fabrication methods. In very thin nanowire structures (sub-micron-meter in width), additive piezoresistance patterning and fabrication can be highly difficult and thus need to be avoided. This invention shows that, in piezoresistive nanowires with homogeneous material composition and symmetric structures, no conventional and additive piezoresistance loops are needed. Using AC and DC drive signals, and bias signals of controlled frequency and amplitude, output signals having a variety of frequencies can be obtained. Various examples of such resonators and their theory of operation are described.

Abstract: A surface mount piezoelectric oscillator includes a piezoelectric resonator with a container main body, a plurality of external terminals, a mounting board with an IC chip, a plurality of connecting terminals, and a solder ball. The solder ball bonds the plurality of external terminals and the plurality of connecting terminals by melting and hardening. The solder bonding portion has approximately a circular shape with approximately a same size as a size of the connecting terminal of the mounting board. The solder ball placed on the connecting terminal of the mounting board is melted, self-aligned, and hardened so as to form a solder fillet of nearly axial symmetry. The solder fillet bridges between the both electrodes and bonds the connecting terminal of the mounting board and the solder bonding portion of the external terminal of the piezoelectric resonator.

Abstract: Methods and apparatuses for Micro-Electro-Mechanical Systems (MEMS) resonator to monitor the platform temperature. Fabricating the resonator on a relatively low cost flexible polymer substrate rather than silicon provides mechanical flexibility as well as design flexibility with respect to sensor placement. Sensor readout and control circuits can be on silicon if desired, for example, a positive feedback amplifier to form an oscillator in conjunction with the resonator and a counter to count oscillator frequency.

Abstract: A clock generator is disclosed for use with an oscillator device. The clock generator may include a signal conditioning pre-filter and a comparator. The signal conditioner may have an input for a signal from the oscillator device, and may include a high pass filter component and a low pass filter component. The high pass filter component may pass amplitude and frequency components of the input oscillator signal but reject a common mode component of the oscillator signal. Instead, the high pass filter component further may generate its own common mode component locally over which the high frequency components are superimposed. The low pass filter component may generate a second output signal that represents the locally-generated common mode component of the first output signal. The clock generator may have a comparator as an input stage which is coupled to first and second outputs of the filter structure.

Abstract: A vibrating member includes a base portion, a plurality of vibrating arms which extend from one end portion of the base portion, are provided in parallel in a first direction, and extend in a second direction perpendicular to the first direction, a linking portion which is provided between the base end portions of two adjacent vibrating arms and extends from the other end portion of the base portion, and a support portion which is connected to the base portion through the linking portion.

Abstract: A MEMS resonator has a component which provides a capacitance associated with the transduction gap which has a temperature-dependent dielectric characteristic, which varies in the same direction (i.e. the slope has the same sign) as the Young's modulus of the material of the resonator versus temperature. This means that the resonant frequency is less dependent on temperature.

Abstract: Oscillator circuits include a MEMs resonator, a variable impedance circuit (e.g., varistor) and an adjustable gain amplifier. The variable impedance circuit includes a first terminal electrically coupled to a first terminal of the MEMs resonator and the adjustable gain amplifier is electrically coupled to the variable impedance circuit. The adjustable gain amplifier may have an input terminal electrically coupled to the variable impedance circuit and a second terminal of the MEMs resonator may receive, as feedback, a signal derived from an output of the adjustable gain amplifier. A Q-factor control circuit may be provided, which is configured to drive the variable impedance circuit and the adjustable gain amplifier with first and second control signals, respectively, that cause an impedance of the variable impedance circuit and a gain of the adjustable gain amplifier to be relatively high during a start-up time interval and relatively low during a post start-up time interval.

Abstract: A MEMS resonator has a resonator mass in the form of a closed ring anchored at points around the ring. A set of ring comb electrode arrangements is fixed to the ring at locations between the anchor points, to couple the input (drive) and output (sense) signals to/from the resonator mass.

Abstract: The present invention relates to an oscillator. The oscillator includes a resonator unit configured to resonate terahertz waves generated by an active layer using intersubband transitions of a carrier. The oscillator further includes a strain generating unit configured to generate strain of the active layer. Still furthermore, the oscillator includes a control unit configured to control the strain generating unit in accordance with the oscillation characteristic (the frequency or the output) of the terahertz waves resonated by the resonator unit.

Abstract: A SAW device includes a SAW chip formed of a piezoelectric substrate and an IDT formed thereon, a base substrate that supports the SAW chip, and a fixing member that fixes the SAW chip to the base substrate. The SAW chip that forms a cantilever is supported by the base substrate via the fixing member in a position where the IDT does not overlap with the fixing member in a plan view of the SAW chip. The length W of the SAW chip in a y-axis direction and the length D of the fixing member in the y-axis direction satisfy 1<D/W?1.6. The fixing member bonds the lower surface and side surfaces of the fixed end of the SAW chip to the base substrate.

Abstract: An electromechanical resonating structure, including: first level major elements coupled to each other to form a second or higher level hierarchy; and first level sub-micron size minor elements with a characteristic frequency and coupled to each of the first level major elements to form a second level hierarchy in which a signal is effectively amplified by vibrating each of the plurality of major elements in at least one mode determined by the geometry and dimensions of the first level sub-micron minor elements.

Abstract: A sensor for detecting analytes, a method of making the sensor, and a method of using the sensor. In one embodiment, the present invention comprises at least one array comprising a plurality of resonators. The resonators can be arranged in a plurality of rows and a plurality of columns, and can be connected in a combined series-parallel configuration. The resonators can be adapted to vibrate independently at about the same resonance frequency and about the same phase. The sensor can also comprise an actuator and a signal detector electrically coupled to the array. The sensor can also further comprise an analyte delivery system and can be functionalized for detection of at least one analyte.

Abstract: A tunable resonator is provided that has a high Q for each resonate frequency. The tunable resonator is a MEMs tunable resonator wherein the tuner is affected by moving a moveable mass, associated with the resonating portion of the resonator, form a first position to a second position such that the moveable mass is held in the first position or second position by a detent rather than a constant electromagnet magnetic or electrostatic force applied thereon.

Abstract: A frequency selection device comprises an oscillator, which comprises a resonator mass which is connected by a spring arrangement to a substrate, and a piezoresistive element for controlling oscillation of the resonator mass, which comprises a piezoresistive element connected to the resonator mass. A current is driven through the piezoresistive element to control oscillation of the resonator mass. An input is provided for coupling a signal from which a desired frequency range is to be selected, to the resonator mass; and a detector is used for detecting a signal amplified by the oscillator.

Abstract: A piezoelectric device includes an integrated circuit (IC) chip and a piezoelectric resonator element, a part of the piezoelectric resonator element being disposed so as to overlap with a part of the IC chip when viewed in plan. The IC chip includes: an inner pad disposed on an active face and in an area where is overlapped with the piezoelectric resonator when viewed in plan; an insulating layer formed on the active face; a relocation pad disposed on the insulating layer and in an area other than a part where is overlapped with the piezoelectric resonator element, the relocation pad being coupled to an end part of a first wire; and a second wire electrically coupling the inner pad and the relocation pad, the second wire having a relocation wire and a connector that penetrates the insulating layer, the relocation wire being disposed between the insulating layer and the active face.

Abstract: A MEMS vibrator includes: a substrate; a first electrode disposed above the substrate; and a second electrode disposed in a state where at least one portion of the second electrode has a space between the first electrode and the second electrode, and having a beam portion capable of vibrating, in the thickness direction of the substrate, with electrostatic force and a supporting portion supporting one edge of the beam portion and disposed above the substrate, wherein a supporting side face of the supporting portion supporting the one edge has a bending portion which bends in plan view from the thickness direction of the substrate, and the one edge is supported by the supporting side face including the bending portion.

Abstract: The invention relates to a micromechanical resonator arrangement, in particular micro-mirror scanner with an inner actuator, which comprises an oscillation body capable of oscillation about at least one axis, and with an outer actuator with an oscillating part. The inner and outer actuator form a coupled oscillation system, and the outer actuator is driven by an external drive whose drive frequency is selected in a manner such that the oscillation body of the inner actuator oscillates with one of its eigenmodes or close to this eigenmode. The inner actuator is at least one vacuum-encapsulated micro-actuator chip which is fastened on the oscillating part of the outer actuator.

Abstract: The invention provides MEMS oscillator designs in which the thermal actuation and piezoresistive detection signals are separated. A first approach splits the frequency of the loop into two distinct components, an actuation frequency and a detection frequency. A second approach modifies the design of the MEMS resonator such that the actuation signal follows a different path through the MEMS resonator than the detection signal.

Abstract: A MEMS resonator system that reduces interference signals arising from undesired capacitive coupling between different system elements. The system, in one embodiment, includes a MEMS resonator, electrodes, and at least one resonator electrode shield. In certain embodiments, the resonator electrode shield ensures that the resonator electrodes interact with either one or more shunting nodes or the active elements of the MEMS resonator by preventing or reducing, among other things, capacitive coupling between the resonator electrodes and the support and auxiliary elements of the MEMS resonator structure. By reducing the deleterious effects of interfering signals using one or more resonator electrode shields, a simpler, lower interference, and more efficient system relative to prior art approaches is presented.

Abstract: A MEMS resonator includes a beam oscillator that oscillates mechanically when an electrostatic force is applied. A supporter oscillates along with the oscillator and supports the oscillator; and at least one electrode includes an opposing face to the oscillator across a gap, wherein an electric current generated by the oscillation of the oscillator is output through an output terminal connected with the oscillator or electrode. The oscillator oscillates in a torsional resonance mode with a center being a longitudinal axis of the oscillator, and opposing faces of the oscillator and the electrode are made of semiconductors of which the conductive types are different from each other. Additionally, a surface part of the oscillator including the opposing face is doped with an impurity at a higher density than other part of the oscillator.

Abstract: The device (10) comprises a cylindrical resonator (R) vibrating in extension-compression along its longitudinal axis (?) and having a vibration node (N) in its mid-plane (?), the vibration naturally generating radial extension/compression deformations, and a mechanical decoupling module comprising a hollow cylinder (2) surrounding the resonator and a membrane (1) positioned in the aforementioned mid-plane and rigidly connected to the cylindrical surface of the resonator and to the internal cylindrical surface of the hollow cylinder. The hollow cylinder vibrates in extension/compression in antiphase with the vibration of the resonator, enabling the effects of the radial deformations of the hollow cylinder and of the resonator to compensate each other in an area (ZF) located on the external surface of the hollow cylinder close to the mid-plane.

Abstract: An improved method of packaging a sensor is provided. The method includes the step of affixing a tuning fork to a platform. The tuning fork includes tines comprising one or more surfaces, with each tine further comprising an electrode and a piezoelectric material. An application specific integrated circuit (ASIC) is affixed to the platform. Electrical communication between the ASIC and the electrode of each tine is established for providing stimulus to the tuning fork and for receiving a response signal from the tuning fork. A protective layer is applied to cover the platform and a portion of the tuning fork while maintaining a portion of a surface of each tine free from the protective layer such that the surface can displace the fluid in contact therewith.

Abstract: Systems and methods for operating with oscillators configured to produce an oscillating signal having an arbitrary frequency are described. The frequency of the oscillating signal may be shifted to remove its arbitrary nature by application of multiple tuning signals or values to the oscillator. Alternatively, the arbitrary frequency may be accommodated by adjusting operation one or more components of a circuit receiving the oscillating signal.

Abstract: An oscillator circuit includes an amplifier including at least two terminals for receiving a crystal and an automatic amplitude control loop coupled to the amplifier including biasing circuitry switched between a first operational mode and a second operational mode. The first operational mode occurs during an initial time period and the second operational mode occurs after the initial time period is expired. The biasing circuitry includes first and second PMOS transistor circuits, each transistor circuit including an unswitched PMOS transistor and a switched PMOS transistor. Alternatively, the biasing circuitry can include first and second NMOS transistor circuits, each transistor circuit including an unswitched NMOS transistor and a switched NMOS transistor. The biasing circuitry is under control of an internally generated control signal.

Abstract: A MEMS resonator comprises a resonator body (34), and an anchor (32) which provides a fixed connection between the resonator body (34) and a support body. A resistive heating element (R1,R2) and a feedback control system are used to maintain the resonator body (34) at a constant temperature. A location for thermally coupling the anchor (32) to the resistive heating element (R1,R2) is selected which has a lowest dependency of its temperature on the ambient temperature during the operation of the feedback control.

Abstract: Methods and apparatus for calibration and temperature compensation of oscillators having mechanical resonators are described. The method(s) may involve measuring the frequency of the oscillator at multiple discrete temperatures and adjusting compensation circuitry of the oscillator at the various temperatures. The compensation circuitry may include multiple programmable elements which may independently adjust the frequency behavior of the oscillator at a respective temperature. Thus, adjustment of the frequency behavior of the oscillator at one temperature may not alter the frequency behavior at a second temperature.

Abstract: The object of the invention is to provide an improved structure for a microelectromechanical (MEMS) resonator. According to a first aspect of the invention, the resonator structure in accordance with the invention has a characteristic frequency of oscillation in combination with a given mechanical amplitude, whereby to set said mechanical amplitude, in the resonator structure, by way anchoring at an anchor point located at a given point of the resonator structure substrate, a first element is adapted oscillatory and a second element is adapted oscillatory in such a manner that at least one of said first element and of said second element are arranged to oscillate synchronously with regard to said anchor point, whereby the location of said anchor point is selected to be substantially within the joint projection defined by the dimensions of said first and said second element.

Abstract: An oscillator device comprises a resonator mass which is connected by a spring arrangement to a substrate and a feedback element for controlling oscillation of the resonator mass, which comprises a piezoresistive element connected between the resonator mass and the substrate. The invention provides an oscillator device in which the two parts (resonator and circuit to close the oscillation loop) are combined inside one single oscillator device, which can be a MEMS device.

Abstract: In order to provide a MEMS resonator having a higher Q factor, by suppressing losses in high-frequency signals due to barriers of thin-film lamination portions, in cases where there exist junction interfaces (barriers), such as pn junctions, in AC-current input/output lines for a vibrator (1) and electrodes (2, 3), the MEMS resonator is structured such that a DC current is flowed therethrough along with an AC current at the same time, in order to reduce resistance losses applied to the AC current, wherein there are provided DC bias circuits (22, 23, 24) for continuously flowing DC currents through the junction interfaces, in an input-electrode side and/or output-electrode side.