The entire circuit operates as a delta modulator. 15, 3224–3235 (2015). AU, Ref document number: In the embodiments of Figures 15 and 16, a protection diode-established voltage is taken as a Therefore, since this circuit lacks an input for an external time reference, positive feedback is added via RlO between the output of comparator 604 and the positive input, to create hysteresis that induces the circuit to oscillate, thus providing its own time reference. Figure 1. In such cases, either an operational amplifier-based transconductance circuit, or one of several JFET-based (or JFET/op-amp-based) transconductance circuits (as shown in U.S. Patent No.  The transconductance circuit can define a common ground and a signal voltage reference that is not directly connected to the common ground.  In the embodiment shown in Figure 3, the base of the BJT Q2 is connected to the transducer 28 and to the source of the FET Ql as shown, with the emitter of the BJT Q2 being connected to grounded output resistor Rl and with the collector of the BJT Q2 being connected to the power supply 32 and being separated from the drain of the FET Ql by the drain resistor R9. Both outputs represent the transducer signal.  In the embodiment of Figure 20, the circuit 600 is very similar to circuit 500 of Figure 18, and like reference numbers have been used for like components as appropriate. Circuit 400 is similar to that of Figure 13, except that the output of comparator 404 provides a separate DC feedback signal through resistor R3 and C6 for DC circuit offset control. resistor.  Figure 5 shows a piezoelectric transducer 40 in a transconductance circuit 42 having a DC voltage supply 44 that in most respects is identical to the circuit 36 shown in Figure 4, except that a resistor R5 and a capacitor C3 are provided between the non- inverting input of an operational amplifier Ul and a feedback resistor R3, a transconductance resistor R6 being provided between the tap of the resistor R5/capacitor 4.  As shown in Figure 2, a piezoelectric transducer 22 is provided in a transconductance circuit 24 of a first embodiment. The circuit of Claim 26, wherein the feedback elements comprise at least one resistor and one capacitor. Get the latest public health information from CDC: https://www.coronavirus.gov, Get the latest research information from NIH: https://www.nih.gov/coronavirus, Find NCBI SARS-CoV-2 literature, sequence, and clinical content: https://www.ncbi.nlm.nih.gov/sars-cov-2/. The feedback elements may be, e.g., resistors, capacitors or charge-switching circuits. circuit, which in turn generates a digital output.  Figure 21 illustrates a circuit 700 according to another embodiment, wherein the amplifier is configured as a DTSOA-based "delta modulator" with an intrinsic time reference, as in Figure 20, to which is input the signal from a "voltage output mode" piezoelectric transducer circuit, similar to the arrangement in Figure 19. Therefore, what is needed is a system and method that overcomes these significant problems found in the conventional systems as described above. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. To this end, piezoelectric and signal processing techniques were employed to extract the ECG corresponding signal from the piezoelectric output voltage signal. The fourth connector 62 may be connected to the piezoelectric transducer contained inside the package structure 54. A feedback element through which the output is sent back to the input line is also provided.  The amplifier 342 impresses a voltage at its negative input which is equal to that at its positive input. WIM system setup on a single lane. 300. The circuit of Claim 1, wherein the amplifier has (-) and (+) power supply lines, and the (-) and (+) protection voltage lines are the amplifier (-) and (+) power supply lines. Thomas L. Szabo, in Diagnostic Ultrasound Imaging: Inside Out (Second Edition), 2014. 22. A motor or solenoid is, strictly speaking, a transducer, becausâ¦ 2006321607, Country of ref document: Frequency diverse signal processing techniques such as split spectrum processing  beneï¬t form wider transducers bandwidth when applied to speckle reduction  and contrast enhancement . Since this is not possible in reality, the circuit DC output can become "stuck" against either the positive or negative end of the power supply, in which case no AC signals are possible, otherwise rendering the circuit totally non-functional. Such high DC outputs could result from DC amplification due to the parallel leakage resistance present in some transducers. Piezoelectric transducer: ( a ) photo of the used transducer and ( b…, Devices and experimental setup: ( a ) three electrode ECG system, ( b…, Measured output signals of ECG and piezoelectric sensors: ( a ) Piezoelectric (PZE)…, Signal processing: ( a ) frequency domain of ECG and piezoelectric output voltages.…, NLM Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. Furthermore, in order to clarify the following discussion, it should be noted that "DC feedback" shall be used herein to describe (negative) feedback signals containing both AC and DC frequency components, whereas "AC feedback" shall be used to describe such signals containing only AC frequency components. The piezoelectric transducer is connected via a transducer line 52 and a capacitor C3 (in a voltage divider portion of the circuit) which provides an AC connection to the signal voltage reference node, as shown in accordance with principles set forth above in relation to Figures 5 and 9. AC gain is set by means of feedback voltage divider R8/R7, which allows a much smaller feedback rectangular wave than the usual full-supply-voltage "high" and "low" size (e.g. Circuit 550 retains most aspects of circuit 500, except for the operation of transducer 402 in a voltage output mode, the addition of an input capacitor C8 at the negative input of Ref document number: voltage. 15. The circuit of Claim 23, comprising at least one feedback element through which the output is sent back to the input line. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. There are a variety of piezoelectric materials that can conduct an electric current, both man-made and natural. 17. The circuit of claim 24, wherein the DTSOA circuit includes a comparator having an input connected to the input line, a buffer field effect transistor (FET) is connected to the transducer, and the feedback element, transducer, and FET are included in a feedback loop connected to the comparator input.  In another embodiment, a discrete time sampled operational amplifier (DTSOA)- based transconductance circuit includes a reference voltage, an input line, a piezoelectric transducer connected from the reference voltage to the input line, and an amplifier receiving signals on the input line and generating one or two outputs based on the transducer signal. within a host microcontroller) can remove the DC offset signal. A piezoelectric force transducer is simply a sensor that detects an applied force, deforms under this force, and then generates an electrical signal at its output terminals. The pressure made on piezoelectric sensor creates an electric signal which ultiâ¦ Both transconductance and voltage output mode circuits are described. in piezoelectric transducer applications where a transducer 335 is connected in the input line, the transconductance amplifier operating voltage, as established at its (+) input, need not always be any particular value, and thus may be set by input protection diodes, which do not form very accurate voltage dividers, except in terms of matching among themselves on the same integrated circuit substrate. No claim element herein is to be construed under the provisions of 35 U.S.C. ' The dielectric can be a piezoelectric ceramic. Simultaneous piezoelectric noninvasive detection of multiple vital signs. In order still to have a time reference after removal of the Tref - driven Because of the ample gain provided by the operational amplifier Ul, the output voltage divider established by the resistors R3 and R5 and the capacitor C3 can amplify the basic transconductance voltage by, e.g., ten.  In any case, returning to Figure 13, the comparator 74 functions as an analog-to digital converter that outputs a digitized signal to processing logic 76. For example, one circuit described herein has an input line and a piezoelectric transducer in the input line, an amplifier receiving signals on the input line and generating an output based on the transducer signal, and at least one feedback element through which the output is sent back to the input line. It is also used in medical diagnostics. More specifically, the first connector 56 may be connected to the drain of the FET and, using the circuit shown in Figure 10 for illustration, may be externally connected, by means of a complementarily- shaped connector, to the line 46 to thereby connect the FET drain to the power supply. When far infrared radiation causes a temperature change (and thus some mechanical strain) in the ceramic, electrical charge migrates from one plate to the other.  Figure 15 illustrates an embodiment of a transconductance circuit 300 which has protection elements for reducing operational amplifier leakage current. Because of the extra gain provided by the BJT Q2 and because its base is connected to the source of the FET Ql, an output feedback voltage divider that is established by resistors R3, R4 and a capacitor C3 can be added so as to amplify the basic transconductance voltage developed across a transconductance resistor R2 by, for example, ten, with this voltage being fed back as a current to the gate of the FET Ql through the transconductance resistor R2.  The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:  Figure 1 is a block diagram of a motion sensing system architecture using a piezoelectric transducer detector system;  Figure 2 is a schematic diagram of a first embodiment of a piezoelectric transducer transconductance circuit;  Figure 3 is a schematic diagram of a second embodiment of a piezoelectric transducer transconductance circuit;  Figure 4 is a schematic diagram of a third embodiment of a piezoelectric transducer transconductance circuit;  Figure 12 shows a circuit that is in many respects identical to that shown in Figure 9 (and that may, in accordance with principles discussed above, also be configured similar to Figure 5 when ac-dc separation is not required) except that the analog operational amplifier Ul is replaced with a discrete time sampled operational amplifier (DTSOA) circuit 70 to save the cost of an analog operational amplifier, and a smoothing capacitor C6 has been added at the output of the DTSOA circuit 70 to smooth the digital output signal. This technique is applicable to piezoelectric transducer applications since the transconductance amplifier operating point or voltage need not be any particular value, and thus may be set by the input protection diodes.  As noted above, Figure 16 illustrates another embodiment of a transconductance circuit 340 with a buffer amplifier 342 that can provide a reference voltage for required circuit functions, e.g. A DTSOA-based differentiator (or "delta-modulator") circuit receives signals on the input line and generates an output. The word âtransducerâ usually refers to a device that performs a conversion between the physical realm and the electrical realm.  Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings. The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or In each circuit, the AC feedback is adjustable somewhat independently by R8 and R7, and the DC feedback is adjustable somewhat independently by R3. connected to the line 48 in Figure 10 to thereby connect the FET source to the portion of the circuit shown.  In an embodiment where the circuit 71 of Figure 13 is a transconductance circuit, the component 72 in Figure 13 is a piezoelectric transducer and is illustrated functionally as a capacitor from the reference voltage line to a comparator 74. The two inputs of amplifier 310 are protected by two diode pairs consisting of diodes 320 and 322, and of diodes 330 and 332, respectively, with each pair connected between positive and negative supply voltages V+ and V-. The power supply 32 is connected to the drain of the FET Ql as shown through a drain resistor RQ. The hollow housing 55 holds the present piezoelectric transducer, FET, and transconductance resistor in any of the circuits shown above. Such sensors advantageously are simple and relatively inexpensive. The piezoelectric detector is incorporated in a transconductance circuit in the embodiments of Figures 2 to 18 and 20, and in a voltage output mode circuit in the embodiments of Figures 19, 21 and 22. See this image and copyright information in PMC. The circuit of Figure 21 provides a low-cost delta-modulator that operates directly from a piezoelectric transducer output and provides a convenient digital signal without requiring the intervening amplification used in prior art. Online digital filter and QRS detector applicable in low resource ECG monitoring systems. International Journal of Telemedicine and Applications 1–11 (2014). S = ây/âx. As the transconductance circuits of Figures 13 and 14 may sometimes be realized with high- impedance amplifiers, it is useful to provide a method of reducing the input leakage current in such amplifiers.  In the circuit of Figure 20, the DTSOA from the embodiment of Figure 12 is opened up and expanded to include the FET 510, and the entire circuit is operated as a delta-modulator. Although it may be simple, the detection of TOA requires complex statistical and signal processing techniques. Conventional ultrasonic imaging requires acoustic scanning over a target object using a piezoelectric transducer array, followed by signal processing to reconstruct the image. Consequently, there is no high frequency limit due to any effect of the FET Ql internal drain-gate capacitance, so a resistor-capacitor pair R9 - C5 shown in the transistor-only circuit of Figure 3 is not required in the circuit 36 of Figure 4. The sampling reference time (Tref) of the processing circuit 76 may be a period much shorter than the time constant created by the feedback resistor and transducer capacitance, so that those components may provide an average direct current voltage corresponding to the percentage of time that the latched voltage output from the processing circuit 76 spends in high versus low states. can be used, as long as the connectors are accessible from outside the housing. Since, on the same integrated circuit substrate, all of the protection diodes are similar, the (-) input protection diodes 330 and 332 independently establish a voltage similar to that established by the reference pair of protection diodes 320 and 322. Figure 11 shows that the piezoelectric transducer, FET, and transconductance resistor may be provided in a single package for convenience, with four connectors such as but not limited to pins being provided on the package to connect the transducer, FET source, FET gate, and transconductance resistor to the circuit described above.  As illustrated in Figure 22, resistor R9 is connected in a feedback loop through transducer 402 and FET 510, rather than directly to the negative input of comparator 704 as in Figure 21. from +5 V to GND). 4. The piezoelectric transducer 22 may take the form of a capacitor, i.e., two electrically conductive plates separated by a dielectric which can be a piezoelectric ceramic. Piezoelectric Sensor Piezoelectric Sensor Specifications. A transducer converts either a driving electric-signal to an acoustic-signal radiating outward or an acoustic-signal arriving at the receiver to an electric-signal (i.e., measured acoustic-signal). The fourth connector 62 may then be connected to the line 52 which, as shown in the illustrative circuit of the Figure 10, connects the piezoelectric transducer at the FET gate to other circuit structure. The power supply 26, which can be from +5 V to GND). If desired, the digital logic circuit can be established by a microcontroller. So far, there has been limited reporting of the transient response of the piezoelectric transducers driven by â¦ Some of the basic characteristics of piezoelectric sensors are. The transconductance circuit 24 has a direct current (DC) voltage supply 26. Show more. resistor R3 and smoothed by capacitor C6 on its way to feedback resistor R6. The rectangular wave is coupled through capacitor C6 to the DTSOA's delta-modulator feedback resistor R9.  In the circuit 800 of Figure 22, the node "transducer/R6/C8/R9" functions as a comparator input of veiy high impedance (that of the FET gate), which allows, in practical designs, the use of higher impedance values for C8 and R9. It is to be understood that the physical connector arrangement shown in Figure 10 is exemplary only, and that other connector arrangements (e.g., one connector on each of four sides of the housing 55) may be implemented. Also, as shown the transistor Q3 passes the FET drain-to-source output current to the base of the NPN transistor Q4, where, because of the gain of the transistor Q4, a proportionately larger transistor output current (collector-emitter current) is developed that is in turn converted back to a voltage by a load resistor that is connected to the power supply voltage. Such separate control of AC and DC circuit gain, by means of a resistor/capacitor network, can be added to the circuits of Figures 12 and 13. One feedback element circuit may be designed to pass only AC signals, whereas another may be designed to pass both AC and DC components. The rectangular wave is coupled through capacitor C6 to the DTSOA's delta-modulator feedback resistor R9.  Figure 19 illustrates a circuit 550 similar to the circuit 500 of Figure 18, except that a voltage-mode transducer circuit is substituted for the transconductance circuit. as a reference input for capacitor (or transducer) 335. COVID-19 is an emerging, rapidly evolving situation. The transconductance current summing node is at the gate of the FET Ql, which buffers the inverting input of the operational amplifier Ul. In the reverse-biased condition, the diodes act as very-high- value resistors. It is siâ¦ -, Cooper J. Electrocardiography 100 years ago. Schematic overview of the presented approach. USA.gov. High amplification ECG, signal averaging technic, frequency analysis and intracardiac mapping]. EP, Kind code of ref document: comparator 552, and the connection of an additional feedback resistor R9 at the negative input of comparator 552. Mechanical Systems and Signal Processing. This principle is exploited in piezoelectric force measurement technology. 3. In this paper, the revolutionary generation and extraction of the corresponding ECG signal using a piezoelectric transducer as alternative for the ECG will be discussed. In this embodiment, a protection diode-established voltage is taken as a reference, and transferred to a principal- function circuit input (in this example, a transducer's transconductance amplifier summing node, which is operated at a constant voltage), such that the input operates at a voltage exactly (or very nearly) equal to the voltage established by its own protection diodes, thus causing the minimum amount of current to flow into or out of its protection diodes into the principal-function circuit. In non-limiting embodiments the piezoelectric transducer can be connected to the input line of the discrete time sampled operational amplifier circuit. "D" latch 406, positive feedback through voltage divider RlO / (Rl II R2) promotes predictable circuit oscillation. Figure 1. The comparator output is used both for AC and DC feedback. a five volt power supply established by one or more dry cell batteries, is connected to the drain of the FET Ql as shown.  Figure 18 shows a circuit 500 that is similar to circuit 400, and like reference numbers have been used for like components as appropriate. 20. A configurable and low-power mixed signal SoC for portable ECG monitoring applications. By "standard input impedance" is meant an impedance of no more than 107 Ohms. The most well known, and the first piezoelectric material used in electronic devices is the quartz crystal. 19, 82–91 (2015). This node is at a voltage Vref between V+ and V-. The circuit shown in Figure 13 performs substantially identically to an analog transconductance circuit, with the exception that its output is digital, in the form of low or high voltages that are determined at each time-sampling.  With the above four-connector, three component package, the exceedingly small currents that are associated with very high resistances, such as a typical transconductance resistor of 125 G Ohms, are all contained inside of the housing 55.  Figure 22 is a schematic diagram of a modified version of the voltage-mode circuit of Figure 21. many embodiments of discrete time sampled operational amplifier circuits are contemplated herein, including the embodiment shown in Figure 13. The rectangular wave is coupled through capacitor C6 to the transconductance feedback resistor R6. CS pair and the gate of the FET Ql. It is used in electric lighter used in kitchens. An additional feedback resistor R9 is connected to the negative input of comparator 704. A discrete time sampled operational amplifier circuit is operably engaged with the piezoelectric transducer. The circuit may be a discrete time sampled operational amplifier (DTOA) based transconductance or 'voltage output mode' circuit. A Wireless Emergency Telemedicine System for Patients Monitoring and Diagnosis. [Methods for the detection of ventricular late potentials.  Figure 5 is a schematic diagram of a fourth embodiment of a piezoelectric transducer transconductance circuit;  Figure 6 is a schematic diagram of a modified version of the first embodiment shown in Figure 2, wherein the alternating current (AC) and direct current (DC) connections to the transducer are separated from each other to avoid DC outputs that, if sufficiently high, might otherwise saturate the circuit;  Figure 7 is a schematic diagram of a modified version of the second embodiment shown in Figure 3, wherein the AC and DC connections to the transducer are separated from each other;  Figure 8 is a schematic diagram of a modified version of the third embodiment shown in Figure 4, wherein the AC and DC connections to the transducer are separated from each other;  Figure 9 is a schematic diagram of a modified version of the fourth embodiment shown in Figure 5, wherein the AC and DC connections to the transducer are separated from each other;  Figure 10 is a schematic diagram of still another alternate embodiment of a piezoelectric transducer transconductance circuit;  Figure 11 is a perspective view of a transducer package;  Figure 12 is a schematic diagram of a modified version of the fourth embodiment shown in Figure 9, using a discrete time sampled operational amplifier in lieu of an analog operational amplifier;  Figure 13 is a schematic diagram of a non-limiting discrete time sampled operational amplifier-based transconductance circuit according to another embodiment;  Figure 14 is a schematic diagram a non-limiting discrete time-sampled differentiator circuit with a conventional transconductance circuit at its input, according to another embodiment;  Figure 15 is a schematic diagram of a transconductance circuit according to another embodiment having an amplifier input leakage current reduction circuit;  Figure 16 is a schematic diagram of a transconductance circuit according to another embodiment with an alternative amplifier input leakage current reduction circuit;  Figure 17 is a schematic diagram of a piezoelectric transducer circuit with separate.