220results about How to "Increase output impedance" patented technology

A feedthrough terminal assembly for an active implantable medical device (AIMD) includes a plurality of leadwires extending from electronic circuitry of the AIMD, and a lossy ferrite inductor through which the leadwires extend in non-conductive relation for increasing the impedance of the leadwires at selected RF frequencies and reducing magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires. A process is also provided for filtering electromagnetic interference (EMI) in an implanted leadwire extending from an AIMD into body fluids or tissue, wherein the leadwire is subjected to occasional high-power electromagnetic fields such as those produced by medical diagnostic equipment including magnetic resonance imaging.

A wireless communications system optimizes performance by dividing communications functionality between a wireless pacemaker and a wireless monitoring base station according to the design constraints imposed by the system elements. Typical design constraints include high frequency operation, low pacemaker power consumption, reasonable range, high data rate, minimal RF radiation of internal circuitry, small pacemaker antenna system, simple pacemaker RF circuit design, high reliability, low pacemaker cost, and use of existing pacemaker construction methodologies.

An interface apparatus for fan monitoring and control includes a current source amplifier that generates a programmable current in response to its input voltages. Associated with an output capacitor, which is able to reduce noise, the programmable current drives the fan at a desired speed. The rotating fan induces a ripple signal in the output capacitor, which is fed to a band-pass amplifier to produce a tachometer pulse. Through a buffer amplifier, an input control signal combined with a thermal sensor signal has direct control over the current source amplifier. Alternatively, a PWM circuit having a comparator, a ramp oscillator and the output of the buffer amplifier drives the current source amplifier in switching mode. Since the ramp oscillator can be synchronized by the input, both analog and pulse signals can function as the input control signals.

A method and system for providing a mixed-mode (current- and voltage-source) audio amplifier is disclosed. The mixed-mode amplifier includes a voltage sensing feedback path including a first network comprising at least one circuit; and a current sensing feedback path including a second network comprising at least one circuit. According to the method and system disclosed herein, the first and second networks vary an output impedance or transconductance of the amplifier as a function of frequency of the input voltage signal, such that at a first frequency range, the amplifier operates substantially as a current amplifier, and at a second frequency range, the amplifier operates substantially as a voltage amplifier, thereby inheriting distortion reduction of the current amplifier and stability of the voltage amplifier.

An electroacoustic transducer includes a condenser microphone, which includes a package having a cavity and a through-hole, a plate whose thickness is thinner than the length of the through-hole and which has a sound hole overlapping with the through-hole in plan view, and an electroacoustic transducer die, which is stored in the cavity of the package. The electroacoustic transducer die includes a fixed electrode and a diaphragm electrode, which are positioned opposite to each other and which are supported by and enclosed inside of a support. The sound hole of the plate is reduced in dimensions realizing a small sectional area and a small depth, thus realizing a high resonance frequency higher than the audio frequency range.

A semiconductor die with an integrated circuit providing a signal conditioner (106) for a capacitive transducer (105), comprising: a gain stage (101) configured to receive an analogue transducer signal; an analogue-to-digital converter (102) coupled to receive a signal outputted from the gain stage (101) and to provide a digital signal. A feedback signal is provided via a digital-to-analogue converter (104) and a digital signal processor (103) that receives the digital signal; and the gain stage (101) is configured with a first input (107) and second input (108) coupled to receive the analogue transducer signal and the feedback signal, respectively.

In a SAW-less receiver involving a passive mixer, novel degenerative impedance elements having substantial impedances are disposed in incoming signal paths between the differential signal output leads of a low-noise amplifier (LNA) and the differential signal input leads of the passive mixer. The passive mixer outputs signals to a transimpedance amplifier and baseband filter (TIA). Providing the novel degenerative impedance elements decreases noise in the overall receiver as output from the TIA, with only minimal degradation of other receiver performance characteristics. In some examples, the passive mixer receives local oscillator signals having duty cycles of substantially less than fifty percent. In some examples, the degenerative impedance elements can have one of several impedances.

An operational amplifier amplifies a signal received through its input terminal connected directly to a piezoelectric device. A bias voltage generating section includes a voltage divider between the power supply terminal and the ground terminal. The drain and source of a p-channel MOSFET are connected to the input terminal of the operational amplifier and the ground terminal. Since the voltage divider applies a bias voltage to the gate and the backgate, the p-channel MOSFET maintains the OFF state. Since a drain-backgate parasitic diode clamps the drain potential to the bias voltage, the bias voltage is applied to the input terminal of the operational amplifier. Then, the drain-backgate resistance is extremely high. The p-channel MOSFET is embedded on a substrate together with other circuits of the amplification device. Thus, the amplification device with an extremely high input impedance is configured as a single integrated circuit.

The invention belongs to the technical field of engine control and particularly relates to a practical aircraft engine fuel electronic control system. A general closed-loop control system for providing positive and negative constant flow sources for aircraft engines is mainly applied to performance adjustment and static testing for an engine with an electro-hydraulic servo valve being served as an electro-hydraulic conversion device and can be used for primarily calibrating steady state characters of the engine. According to the general closed-loop control system for providing the positive and negative constant flow sources for the aircraft engines, a high-precision measuring module which provides excitation signals for an LVDT (Linear Variable Differential Transformer) collects a current position of the LVDT, a preset instruct state of the closed-loop system is changed, PID (Proportion Integration Differentiation) calculation is performed on the current position and a preset position of the LVDT under a closed-loop control state, and the flow of the engine is controlled. The closed-loop control system needs to maintain current values to be at steady state values during a testing process.

The invention provides a input buffer circuit for high-speed pipeline analog-to-digital converter (ADC). The input buffer circuit comprises an input pair transistor, a current mirror load, a gain-boosted amplifier and a compensation capacitor, wherein the input pair transistor consists of a first MOS (metal oxide semi-conductor) transistor and a second MOS transistor of a source negative-feedback resistor; the current mirror load consists of a third MOS transistor and a fourth transistor which are connected to each other by a gate; the positive input terminal of the gain-boosted amplifier is connected with the drain of the first MOS transistor, the negative input terminal thereof is connected with the drain of the second MOS transistor, and the output terminal thereof is connected with the gate of the third MOS resistor; and one terminal of the compensation capacitor is connected with the gate of the third MOS transistor, and the other terminal thereof is connected with the drain of the third MOS transistor. The input buffer circuit of the invention is capable of meeting the requirements for the input of high-speed signals, effectively reducing the inputted load capacitance and increasing the outputted impedance.

In an elastic wave acoustic device, input ends of first to third longitudinally coupled resonator surface acoustic wave filters are connected to an unbalanced signal terminal, the output end of the first longitudinally coupled resonator surface acoustic wave filter, and a first IDT defining a first output terminal of the second longitudinally coupled resonator surface acoustic wave filter are connected to a first balanced signal terminal, the output end of the third longitudinally coupled resonator surface acoustic wave filter, and a third IDT defining a second output terminal of the second longitudinally coupled resonator surface acoustic wave filter are connected to a second balanced signal terminal, and the phase of an output signal to an input signal of the first longitudinally coupled resonator surface acoustic wave filter differs by about 180 degrees from the phase of an output signal to an input signal of the third longitudinally coupled resonator surface acoustic wave filter. Thus, the elastic wave filter device has a balanced-to-unbalanced conversion function and an impedance conversion function, and reduces an insertion loss within a passband.

The invention discloses a low noise amplifier with adjustable gain. The low noise amplifier provided by the invention is characterized in that two groups of cascode tubes are crossed and connected in parallel on a main body cascode tube; the amplified current of a transitron is crossed and shunted; partial radio frequency (RF) input positive current flows to a negative output end; and partial RF input negative current flows to a positive output end, thus a gain control circuit which can adjust the gain of the low noise amplifier is formed through crossed cancellation. Compared with the traditional method for controlling the gain of the low noise amplifier, the low noise amplifier with adjustable gain has the characteristics that the system noises is not increased when the gain is adjusted, the gain control is accurate, the bias and input impedance are not influenced, and the power consumption is not increased.

The invention discloses a multifrequency synchronous excitation current source used in bio-electrical impedance frequency spectrum measurement, which comprises a multifrequency synchronous signal generating module, a unipolar-bipolar conversion module, and a voltage control current source module in sequential connection, wherein the multifrequency synchronous signal generating module adopts an FPGA (Field Programmable Gate Array) as a carrier, performs hardware programming through utilizing a Verilog HDL (Hardware Description Language), generates unipolar MFS voltage signal V FPGA based on finite state machine principles, and inputs the signal V FPGA to the unipolar-bipolar conversion module; the unipolar-bipolar conversion module is used for converting unipolar MFS voltage signal V FPGA into symmetric bipolar MFS voltage signal V OUT, and inputting the signal V FPGA into the voltage control current source module; and the voltage control current source module is used for converting the bipolar MFS voltage signal V OUT output by the unipolar-bipolar conversion module into bipolar MFS current signal IOUT and directly exerting the bipolar MFS current signal IOUT onto a tested biomass target receiving BIS (Bispectral) measurement. The multifrequency synchronous excitation current source provided by the invention lays a foundation for the realization of BIS multifrequency synchronous measurement.

A device for measuring impedance of biological tissue may include electrodes and a voltage-to-current converter coupled to the electrodes to drive an alternating current (AC) through the tissue and sense an AC voltage. The converter may include an amplifier having first and second inputs and an output, a first voltage divider coupled to the first input, a second voltage divider coupled to the second input, a filter capacitor coupled between the output and the second voltage divider, a current limiting resistor coupled between the second input the second voltage divider, and a bypass capacitor coupled to the second input of the amplifier and in parallel with the resistor. A single-ended amplitude modulation (AM) demodulator may demodulate the AC voltage and generate a corresponding baseband voltage representing the impedance. The device may also include an output circuit to generate output signals representative of DC and AC components of the baseband voltage.

The invention belongs to the technical field of integrated circuits, in particular to a high-speed low-power consumption large-swing operational amplifier for an analog-digital converter of a production line. The operational amplifier consists of an input tail current source tube, differential input geminate transistors, an N-type co-gate tube, a P-type co-gate tube, a P-type load tube, a duplicate circuit and a bootstrap circuit. A gain-boosting sleeve type cascade structure is adopted, so the tail current source tube and the PMOS load tube work in a linear area to increase the output swing; and the duplicate circuit dynamically regulates the grid voltage of the tail current source to maintain constant current and increase output impedence so as to improve the common-mode rejection ratio and the power rejection ratio. The operational amplifier realizes high speed, low power consumption, large output swing, high common-mode rejection ratio and high power rejection ratio.