582 results about "Input resistance" patented technology

A self-powered current monitor for monitoring current in electric power systems. Various data relating to input currents may be displayed, such as current magnitude, current demand, and harmonics levels. Operating power is derived from one or more of the input currents. The power supply configuration may include a burden-reducing means to reduce the burden on input current sources during sampling of the input currents. The self-powered current monitor (1) includes a power supply section (3), input resistors (R1 and R3), an analog-to-digital converter circuit (5), a microprocessor circuit (6), a memory circuit (9), and a display circuit (7). Optional features include a burden-reducing circuit (2), input circuit protective elements (D1, D2, D3, D4, R2, and R4), an amplifier circuit (4), a user interface circuit (10), and an interface circuit (8) for communication to other equipment.

In at least one embodiment, a controller allows triac-based dimmer to properly function and dim a load whose voltage is regulated by a switching power converter. In at least one embodiment, the switching power converter includes a switch to control voltage conversion of an input voltage to the switching power converter, wherein phase delays are introduced in the input voltage by a triac-based dimmer during a dimming period. In at least one embodiment, the controller is configured to control the switch of the switching power converter to establish an input resistance of the switching power converter during a dimming portion of the input voltage, wherein the input resistance allows the triac-based dimmer to phase modulate a supply voltage to the dimmer so that an output voltage of the dimmer has a substantially uninterrupted phase delay during each half-cycle of the supply voltage during the dimming period.

A self-calibrating test probe system of the present invention does not require probing head removal and replacement. Using the system of the present invention, the test probe and / or the entire system (including a testing instrument) may be calibrated or may self-calibrate while the probing head remains connected to an electrical component under test. The self-calibrating electrical testing probe system includes calibration circuitry including at least one input resistor, at least one relay, and at least one known calibration reference signal. If the test probe is an active test probe, the calibration circuitry may also include at least one amplifier. Each relay has a first position that provides signal access to a testing signal from an electrical component under test and a second position that provides signal access to the known calibration reference signal. Using the present invention, the error of the test probe and / or system is determined and compensated. Exemplary methods by which error compensation may be provided includes, for example, amplifying the testing signal, creating a correction table of correction values and adding an appropriate value from the correction table, or mathematically compensating.

A method of driving a display panel includes applying a common voltage to the display panel, sensing a frequency of the display panel to generate a frequency signal, adjusting a gain of an operational amplifier based on the frequency signal, receiving a feedback common voltage from the display panel, and compensating the common voltage using an input resistor, the operational amplifier and a feedback resistor based on the feedback common voltage to apply the compensated common voltage to the display panel. The operational amplifier includes an inverting input terminal connected to the input resistor, a non-inverting input terminal to which a reference common voltage is applied and an output terminal. The feedback resistor is between the inverting input terminal and the output terminal.

The invention discloses a complementary metal oxide semiconductor (CMOS) automatic gain control amplifier for canceling direct current offset. The CMOS automatic gain control amplifier comprises a cascade amplification link, an automatic gain control feedback loop and a direct current offset canceling feedback loop. The cascade amplification link uses multistage variable gain amplification units for cascading and can achieve high gain and enlarge high gain dynamic ranges. The automatic gain control feedback loop uses a charge pump structure and has the advantages that the automatic gain control feedback loop is less influenced by process deviation and temperature deviation, is capable of accurately detecting narrow-band and wide-band signal amplitude and is suitable for achieving CMOS processes. The direct current offset canceling feedback loop uses two-stage negative feedback loops, and each of the two-stage negative feedback loops uses an integrator as low-pass negative feedback; an active device is used as an integrator input resistor, and an equivalent resistor is provided with characteristics of temperature compensation; and the automatic gain control amplifier for canceling the direct current offset is capable of effectively canceling the direct current offset superposed by a preceding stage circuit and the direct current offset of the amplification link and is provided with a lower high pass corner frequency and a higher integrated level, and the automatic gain control amplifier for canceling the direct current offset is small in low-frequency signal loss and requires no off-chip passive devices (high value resistors or capacitors and the like). The automatic gain control amplifier is applicable to wireless communication receivers with zero intermediate frequency structures in the CMOS processes.

An amplifier circuit for capacitive transducers, such as miniature electret or condenser microphones, wherein the amplifier circuit comprises bias control means adapted to improve settling of the amplifier circuit. Another aspect of the invention relates to a miniature condenser microphone and a monolithic integrated circuit comprising an amplifier circuit according to the present invention. The present invention provides amplifier circuits of improved performance by resolving traditionally conflicting requirements of maintaining a large input resistance of the amplifier circuit to optimize its noise performance and provide fast settling of the amplifier circuit.

An amplifier circuit for capacitive transducers, such as miniature electret or condenser microphones, wherein the amplifier circuit comprises bias control means adapted to improve settling of the amplifier circuit. Another aspect of the invention relates to a miniature condenser microphone and a monolithic integrated circuit comprising an amplifier circuit according to the present invention. The present invention provides amplifier circuits of improved performance by resolving traditionally conflicting requirements of maintaining a large input resistance of the amplifier circuit to optimize its noise performance and provide fast settling of the amplifier circuit.

A circuit for audio amplification includes an amplifier and a first input resistor. The amplifier is arranged to provide an amplifier output signal that is based, in part, on a capacitively-coupled audio input signal. The capacitively-coupled audio input signal is based, in part, on an input RC value. The input RC value is given by the input capacitance times the input resistance. The input resistance is reduced during the turn-on in order to achieve a fast turn-on time with minimal pop-and-click noise. Also, the input resistance is increased to its normal value after the turn-on so that full audio fidelity is substantially maintained during normal operation.

A voltage acquisition circuit for sensing input voltage signals in each phase of an electrical service includes a non-active current transformer configuration that is operable over a wide input voltage range. The current transformer configuration includes primary and secondary windings, an input resistor and a burden resistor across which an output voltage is defined. The input resistor may be relatively large, such as on the order of about one MΩ and the transformer core may have a nanocrystalline core characterized by predictable magnetic properties versus varied transformer flux levels. This operational predictability facilitates phase compensation via digital filtering or otherwise for any phase shift induced between input and output voltages of the current transformer.

Method and apparatus are provided for high linearity and low noise communication signal mixing. The apparatus includes a high linearity low noise mixer having an input stage coupled to a switch stage by a series-coupled blocking capacitance and input resistance. The input stage includes a buffer with negative feedback, and the switch stage includes a transistor based switch network connected to an amplifier that has feedback resistance and shunting capacitance. The method includes AC coupling an RF signal, increasing a gain of the RF signal, reducing third-order distortion by negatively feeding-back the RF signal, blocking IM2 generated from said gain increasing step, increasing a second-order input intercept point (IIP2) by attenuating the RF signal across a resistance, and applying a local oscillator input to the RF signal.

The invention discloses an oscilloscope with a high-frequency path and low-frequency path separation circuit, comprising a high-frequency path and low-frequency path separation circuit. The high-frequency path and low-frequency path separation circuit comprises an attenuation switch circuit, a high-frequency path circuit and a low-frequency path circuit, wherein the input signal of the oscilloscope enters the attenuation switch circuit and is switched by a double-pole-double-throw switch in the attenuation switch circuit; then the input signal enters the high-frequency path circuit and the low-frequency path circuit; the input signal of the oscilloscope is output respectively from the high-frequency path circuit and the low-frequency path, the ratio of a high-frequency output signal and a high-frequency input signal is 1:1, the ratio of a low-frequency output signal and a low-frequency input signal is 1:1, i.e. the ratio of signal input and signal output is 1:1 follow; and thus, the separation process of high-frequency components and low-frequency components is finished. The invention realizes an oscilloscope input circuit with high input resistance, low input capacitance, high DC(Direct Current) precision, high input pressurization, big bandwidth, low noise, large signal input shift range and good frequency response flatness.

The invention provides a gain-controllable wide-frequency low-noise amplifier, wherein, a state configuration device is used for generating input and output configuration signals, gains and wave section switch control signals, respectively controlling an input resistance matching circuit, a gain-controllable wide-frequency low-noise amplifier and an output resistance matching circuit, and setting suitable input resistance, amplifier gain, working bandwidth and output resistance. RF input signals can be transmitted with maximum efficiency to the gain-controllable amplifier through the input resistance matching circuit and generate little energy reflection. Subsequently, owing to the self-adaptability of the amplifier gain, the amplifier adjusts the self-gain according to the input RF signal amplitude, leads the output voltage to be stable, and ensures the normal operation of the sub-step circuit. Owing to the existence of the output resistance matching circuit, the system output signal can be transmitted to the sub-step circuit with the maximum efficiency, thus ensuring the working efficiency of the circuit. The gain-controllable wide-frequency low-noise amplifier of the invention can be applied to the wireless transceiver with different resistance antennas and different working frequency protocols, and can carry out the self-adaptability gain adjustment.

The invention discloses a high-performance D type audio power amplifier adopting high-order multipath feedback structure, which comprises a prepositive variable gain amplifier, an integrator, a pulse width modulation (PWM) circuit, a three-state regulating circuit, a grid driving circuit and a power output stage. The integrator is in a two-order structure formed by cascade connection of two stages of integrators, and two paths of feedback are introduced to form a higher-order double-feedback loop, thereby effectively increasing the loop gain and the out-off-band attenuation, and obviously improving the suppression ratio of total harmonic distortion and noise to power sources and other main properties in the range of audio frequency band (22Hz-22KHz). By introducing two paths of voltage negative feedback and comprehensively considering the input dynamic range, the signal-to-noise ratio and stability factors, the ratio of two stages of feedback coefficients can be regulated by regulating the ratio of the input resistance and the feedback resistance of two stages of integrators, thereby ensuring the stability of a system. The D type audio power amplifier with the structure has the characteristics of high integration level and high performance and can be widely applied to the fields of portable equipment, consumer electronics and the like.

The car power source apparatus is provided with a driving battery 1 that supplies power to the car's electric motor, a voltage detection circuit 3 that measures the voltage of batteries 2 in the driving battery 1, a plurality of voltage detection lines 8 connected in parallel between the input-side of the voltage detection circuit 3 and driving battery 1 voltage detection nodes 9, and a decision circuit 6 that determines if a voltage detection line 8 is open circuited from the voltage measured by the voltage detection circuit 3. Each voltage detection line 8 has a voltage drop resistor 10 connected in series. The voltage detection circuit 3 is provided with input resistors 13 on its input-side. The car power source apparatus makes computations on the voltage measured by the voltage detection circuit 3, which is from the voltage divider formed by the input resistor 13 and voltage drop resistors 10, to detect voltage detection line 8 open circuit.

The invention discloses a circuit and a method for weak current detection and belongs to the current detection field. Geminate field effect transistors are employed by an input end to form a difference amplifier, and I-V conversion of a weak current is carried out; a voltage signal after conversion is sent to two sets of proportion operation circuits having symmetric in-phase input modes for proportion operation amplification; difference operation amplification of the voltage signal after proportion operation amplification is carried out, and a difference operation amplification voltage magnitude is measured. According to the method and the device, the junction type geminate field effect transistors are employed to form the difference amplifier as an input level, so input impedance is improved, and the relatively high common-mode inhibition ratio is acquired; the precise proportion operation circuit structures in the symmetric in-phase input modes are employed as the middle level, input impedance is further improved, and measurement precision is improved; the multiple operation amplifier difference amplification detection technology is employed, conflicts of useful-signal weakness and relatively high common-mode interference can be effectively solved, and high gain, high input resistance and the high common-mode inhibition ratio of the detection circuit are realized.

The invention discloses a high-power pulse current / voltage generating circuit with programmable pulse width, duty ratio and pulse amplitude, wherein a digital-analog converter, an error amplifier, a power amplifier, a pulse current sampling circuit, a pulse voltage sampling circuit, a pulse current / voltage sampling selection switch and a peak detecting circuit are formed into a negative feedback loop. The amplitude analog signal output by the digital-analog converter is compared with the pulse peak obtained by the peak detecting circuit in the error amplifier; and the pulse peak is equal to the amplitude analog signal output by the digital-analog converter in the negative feedback loop. The power amplifier is connected with the output end of the comparator and is connected with the output end of the error amplifier through an input resistor; the comparator adjusts the frequency and duty ratio of the output high-power current / voltage under the control of the periodic pulse signal output by the pulse source, thus, the pulse width, the duty ratio and the pulse amplitude of the output pulse current / voltage of the high-power pulse current / voltage generating circuit can be adjusted.

The invention provides a high-efficiency linear LINC transmitter which comprises a signal preprocessing unit, a signal separation unit, an analogue upconversion unit, an amplifying processing unit and a vector resultant unit, wherein the signal preprocessing unit finishes the segmenting pre-distortion processing for inputted signals and the control of a synthesizer; the signal separation unit divides the signals after pre-distortion into two ways of constant envelope phase-modulated signals; the analogue upconversion unit converts the two ways of separated digital baseband signals into analogue signals, and carries out quadrature modulation to radio frequency; the amplifying processing unit amplifies the power of the two ways of radio frequency signals; and the vector resultant unit synthesizes and outputs the power of the two ways of signals. The signal preprocessing unit can calculate an equilibrium angle theta during signal separation according to the amplitude of the inputted signals and divide the interval of the equilibrium angle theta before signal separation to generate different control signals so as to ensure that the input resistance of the synthesizer changes along with the equilibrium angle theta. In order to guarantee that the LINC transmitter has high linear index, the invention also carries out segmenting pre-distortion processing on the inputted signals according to the interval of the equilibrium angle theta.

The present invention provides a variable gain amplifier, which includes: an operational amplifier; at least one series resistor circuit with one end as a signal input end and the other end connected to the output end of the operational amplifier, and a plurality of resistors connected in series; and A switch circuit connected to multiple nodes of each series resistor circuit and an input terminal of the operational amplifier is used to control the on-off of multiple nodes of each serial resistor circuit and an input terminal of the operational amplifier, so that each Part of the resistance in a series resistance circuit is used as the input resistance of the operational amplifier, and the rest of the resistance is used as the feedback resistance of the operational amplifier; and a decoding circuit is used to decode the input control signal and output it for controlling the operational amplifier. The opening and closing signals of the opening and closing of the plurality of controlled switches. The invention has the advantages of removing the switch circuit from the signal path, thereby eliminating the influence of the on-resistance of each switch on the input impedance and feedback impedance of the operational amplifier, and improving the linearity of the gain.

Programmable filters are used for the purpose of changing the filter cutoff frequency as may be necessary for the operation of a wireless transmitter or receiver. Frequencies may be changed by selecting a desirable value of a capacitor and / or a resistor. The programmable filter controls the frequency according to the disclosed method. Furthermore, in order to reduce the area consumed by the programmable filter a three-dimensional layout is used. In accordance with the disclosed invention it is possible to program the input of the programmable filter to have a higher or lower input resistance as may be required while maintaining the desired programmed cutoff frequency by switching the respective capacitors in a capacitor bank, thereby combining the elements needed for frequency programmability and input impedance level selection.

An amplifier that accurately amplifies signals over a wide bandwidth, including DC, has a voltage-to-current converter, a feed-forward resistive element, a buffer, an input resistive element, a feedback resistive element, and an operational amplifier. A first end of the feed-forward resistive element is coupled to an output of the voltage-to-current converter and to an input of the buffer. A first end of the input resistive element is coupled to an input to the voltage-to-current converter. A first end of the feedback resistive element is coupled to an output of the buffer. An inverting input of the operational amplifier is coupled to a second end of the input resistive element and to a second end of the feedback resistive element. A noninverting input of the operational amplifier is coupled to ground, and an output of the operational amplifier is coupled to a second end of the feed-forward resistive element.

A high voltage operational amplifier input stage utilizes a pair of low voltage p-type MOSFET input devices configured to operate at a common mode voltage. The input stage operates between positive and negative voltage supply rails. Common mode bipolar transistor feedback loops force drains of the MOSFETs to track corresponding source potentials. MOSFET substrate connections are maintained at a predetermined level above (or below, depending on the power supply sensing arrangement) the common mode voltage of the input stage to ensure power supply sensing capability. The input stage has a common mode range which includes the supply rail potential, and which tolerates a total supply voltage that exceeds the MOSFET breakdown voltage. The effective threshold voltage of the input devices is increased above the nominal threshold value to sustain the linear operation of the input stage.

A device for controlling variable speed electric motors, particularly for hand held power tools and other miniaturised electrically powered apparatuses, comprises an electronic driver unit (5) connectable to the terminals (2, 3) of an electric power source for supplying electric current to at least one electric motor (M) and an optical switch device (7) for triggering the electronic driver unit (5). The optical switch device (7) comprises light emitting means (8) and light transducer means (9) for detecting and converting light into an electric variable signal. The light transducer means (9) are operatively connected to the electronic driver unit (5) for controlling the electric motor (M). The light emitter means (8) comprise at least one white light, high brightness LED (D1, D2) connected in parallel to the electric power line terminals (2, 3) by means of a miniaturised power circuit. The miniaturised power circuit comprises at least one resistor (R2) when said at least one electric motor (M) is a DC motor, and a capacitive phase displacement power supply (C, R2) when said electric motor is an AC motor. The capacitive phase displacement power supply (C, R2) comprises at least one capacitor (C) and an input resistor (R2) adapted to supply said diodes (D1, D2) with a threshold voltage.

The invention provides an active differential voltage probe composed of a handle end, a coaxial line and a probe amplifier. The active differential voltage probe provided by the invention has the advantages of higher input resistance, extremely low input capacitance and wider detection bandwidth after the circuit structure is improved. The interference of the probe to a measured signal is less, thus a distortionless detection signal is obtained. Besides, according to the invention, the detection performance of the probe can be further improved by adopting a multipolarity amplifier design method, thus the influence of the length of a probe line on the probe is less, and the frequency response of the probe is good.

A sense amplifier circuit includes a current sense amplifier, a voltage sense amplifier, and an output stabilizing circuit. The current sense amplifier amplifies differential input currents to generate differential output voltages and provides the differential output voltages to a sense amplifier output line pair. The voltage sense amplifier is coupled to the sense amplifier output line pair to amplify the differential output voltages on the sense amplifier output line pair. The voltage sense amplifier is activated at the time later than a time of activation of the current sense amplifier. The output stabilizing circuit is coupled to the sense amplifier output line pair to stabilize the differential output voltages on the sense amplifier output line pair. The output stabilizing circuit has a positive input resistance. Accordingly, the sense amplifier circuit reduces power consumption and an occupied area on a semiconductor chip.

Circuitry is provided for controlling the slew rate of a negative output supply. The slew rate control circuitry includes an NMOS FET, a feedback resistor connected across the drain and the gate of the NMOS FET, an input resistor connected to the gate of the NMOS FET, level shifting circuitry connected between a positive output supply voltage and the input resistor, and a bias current source connected to the gate of the NMOS FET. A negative input supply voltage is connected to the source of the NMOS FET, and the negative output supply voltage is provided across a load connected to the drain of the NMOS FET. As the positive supply voltage ramps up from 0 to +VS, the level shifter provides a voltage to the input resistor that ramps up from −VS to 0 volts. Further, the drain voltage of the NMOS FET ramps down from 0 to −VS, thereby providing a negative output supply voltage −VS with a slew rate that linearly tracks the slew rate of the master positive output supply.

In an embodiment, a sense amplifier can perform a stable differential amplifying operation while having a high differential amplification gain. The sense amplifier comprises a current sense amplification unit, a voltage difference amplification unit, and an output stabilization unit. The current sense amplification unit receives differential input currents and generates differential output voltages corresponding to the differential input currents. The voltage difference amplification unit amplifies a voltage level difference between the differential output voltages through positive feedback using cross-coupled transistors. The output stabilization unit connects output stabilizing elements having a positive input resistance in parallel with the voltage difference amplification unit having a negative input resistance to stabilize the output of the voltage difference amplification unit.

This variable gain amplifier is provided with an operational amplifier. The non-inversion input terminal of the operational amplifier is connected to a reference potential. A feedback resistor is connected between the output terminal and inversion input terminal of the operational amplifier. An input resistor is inserted between the inversion input terminal of the operational amplifier and the input terminal of the variable gain amplifier circuit. An adjustment resistor is connected between the inversion input terminal of the operational amplifier and the reference potential. The resistance value of the adjustment resistor is controlled in such a way as to maintain constant against the resistance value change a combined resistance value in its parallel connection with the input resistor when changing the resistance value of the input resistor.