Abstract: A circuit arrangement for controlling the brightness of at least one LED unit is described by the disclosure. The circuit arrangement, in one example, includes an input for receiving a phase-cut operating voltage from a power supply, a signal processor, connected with the input and adapted to provide a dimming signal for the at least one LED unit from the operating voltage. To allow an efficient reduction of noise in the dimming signal but simultaneously to allow an improved dimming of the LED unit, the signal processor are configured to operate at least in a noise suppression mode and a dimming mode. A control device is provided, connected with the signal processor and configured to set the mode of the signal processor in dependence of the variation in the operating voltage.

Abstract: A bridge-stabilized oscillator with feedback control includes an RF amplifier connected to a first bridge path and a second bridge path. Each first and second bridge path has a variable gain amplifier to receive and modify the respective signals to maintain the resistance of a resistor in the first bridge path, so the resonator in the second bridge path oscillates. A power detector provides a control signal to each of the variable gain amplifiers to maintain the phase of the output with respect to the input and constrain the gain in each of the first and second bridge paths.

Abstract: A self-sustaining ultra-high frequency oscillator and method enable the ability to oscillate and output a signal. A balanced bridge circuit is utilized to null an embedding background response. A first vibrating nanoelectromechanical (NEMS) beam resonator is part of one of the branches of the balanced bridge circuit and determines the frequency of the oscillator's output signal. A feedback loop establishes and sets oscillation conditions of the oscillator's signal. Further, the feedback loop connects an output of the first resonator to an input of the balanced bridge circuit.

Abstract: Disclosed herein is a sine wave oscillator having a self-startup circuit. The sine wave oscillator can start up and output sine waves having a constant frequency without receiving any signals other than supply voltage. The sine wave oscillator includes an operational amplification unit, a first resistor, a first capacitor, a second capacitor, a second resistor, a third resistor, a fourth resistor, and a startup circuit.

Abstract: An amplifier circuit for efficiently driving a tuned resonant load where the amplifier circuit controls the continuously variable resonant frequency of the tuned resonant load so as to match step changes or slower changes in the frequency of the signal with which it is being driven. The circuit includes a tuned resonant load, a driver, a controller and a feedback loop. The driver is coupled to the load and drives it with a driving signal at a frequency under the control of the controller. The controller dynamically controls the resonant frequency of the tuned resonant load in response to an error signal received through the feedback loop. The error signal represents the mismatch in phase between the resonant phase of the load current and the phase of the driving signal, or between the resonant phase of the tuning capacitor voltage offset by 90 degrees and the phase of the driving signal.

Abstract: A tuning circuit includes an oscillator that receives an oscillating input signal and a control signal, and generates an oscillating output signal. The control signal is obtained from a frequency control circuit that compares the phases of the oscillating output signal and a reference signal. The control signal controls the transconductance of a transconductance element in the oscillator, thereby controlling the oscillator output frequency. The oscillating input signal is obtained from an amplitude control circuit that detects an amplitude limit of the oscillator output. The oscillator output amplitude is responsive to the oscillating input signal. Frequency control and amplitude control in this tuning circuit are mutually independent, so their respective control loops remain stable under all frequency and amplitude combinations.

Abstract: An operational amplifier oscillator uses an operational amplifier as a low impedance driver for a resonator, the output from the operational amplifier being a voltage signal at the desired frequency. The operational amplifier has positive and negative feedback paths, with the negative feedback path having a first resistor for driving the impedance at the negative input to a small value when the voltage signal is near a zero crossing and an anti-parallel diode limiter in parallel with the first resistor with an optional series second resistor for driving the impedance at the negative input even smaller when the voltage signal swings away from zero. The positive feedback loop includes a series diode limiter or optional voltage divider. Phase noise is minimized by coupling a filter between the output and the positive feedback path to block the low frequency noise from the positive input of the amplifier.

Abstract: An operational amplifier oscillator uses an operational amplifier as a low impedance driver for a resonator, the output from the operational amplifier being a voltage signal at the desired frequency. The operational amplifier has positive and negative feedback paths, with the negative feedback path having a first resistor for driving the impedance at the negative input to a small value when the voltage signal is near a zero crossing and an anti-parallel diode limiter in parallel with the first resistor with an optional series second resistor for driving the impedance at the negative input even smaller when the voltage signal swings away from zero. The positive feedback loop includes a series diode limiter or optional voltage divider. Phase noise is minimized by coupling a filter between the output and the positive feedback path to block the low frequency noise from the positive input of the amplifier.

Abstract: An active bridge oscillator is formed from a differential amplifier where positive feedback is a function of the impedance of one of the gain elements and a relatively low value common emitter resistance. This use of the nonlinear transistor parameter h stabilizes the output and eliminates the need for ALC circuits common to other bridge oscillators.

Abstract: A simple circuit for converting the resistance variations of a strain gauge measuring bridge into a frequency variation of an oscillator. The circuit includes first and second phase shift circuits connected in cascade in a feedback loop with a frequency-independent device having a variable gain factor F connected in parallel with the first phase shift circuit. The first phase shift circuit includes a high pass filter and a summing amplifier and the second phase shift circuit includes an all-pass filter circuit.

Abstract: A device is provided comprising a circuit using the properties of a resonating cavity sensor whose resonance frequency is modified by the electric capacity variations due to the mechanical deformation of a wall under the effect of the pressure to be measured. It uses a single coaxial cable for connecting the sensor to the user circuit and the sensor, through the coaxial cable, is placed in the leg of an impedance bridge providing the value of the standing wave rate characteristic of the difference between the tuning frequency of the cavity and the frequency of an oscillator controlled by this rate.

Abstract: A sine wave generator circuit for providing, as its output, a substantially perfect sine wave signal includes a multiplier responsive to first input and second input signals of varying magnitude for providing as its output the sine wave signal as a function of the two input signals. There is further included a first feedback circuit path connected between the output and one of the inputs of the multiplier which includes a resistance-capacitance network for providing a phase delayed representation of the output signal as the first of the input signals. The amount of phase delay is determined by the relative values of the resistance-capacitance network and determines the frequency of the sine wave output. Further included is a reference signal the magnitude of which will determine the magnitude of the sine wave output signal. The reference signal is applied to a second feedback circuit path connected between the multiplier output and the other one of its inputs.

Abstract: A notch filter is provided with an ancillary circuit including a non-inverting amplifier and a coupling which enables the filter to form part of an oscillatory loop of which the frequency of oscillation corresponds to the frequency of maximum rejection by the notch filter. Measurement of that frequency facilitates the tuning of the notch filter, which includes capacitors constituted by varactor diodes. The gain of the ancillary circuit may be adjusted to change its mode of operation from oscillation to that of a tuned amplifier so that a sweep of the center frequency of the notch filter through a range of interest facilitates a search for an unknown interfering frequency and the simultaneous tuning of the notch filter to reject that interference.

Abstract: A replica bridge sensing circuit, comprising an amplifier having inverting and non-inverting inputs, which are symmetrically connected to a generator through a bridge circuit that has replica elements in corresponding branches. Replica elements are defined as circuit components which because of identity of the manufacturing process, are nearly identical both physically and electrically. A nearly balanced replica bridge, so connected, between the input and the output of such an amplifier forms a Replica Bridge Oscillator (RBO) circuit. Non-linear elements are included in the oscillator circuit to stabilize the amplifier output amplitude and the phase angles between the inputs and output. Replica Bridge Oscillator operation is substantially immune to changes in environmental conditions and to changes in the power supply voltages.

Abstract: The bridge unbalance of a measuring bridge including a measuring transducer is converted into a frequency variation of an RC-oscillator. Since measuring transducers often have characteristics which are not exactly linear, such a conversion, which exactly compensates for said non-linearity, would be effective. For this purpose, correction voltages are derived from the voltages supplied by the oscillator by means of differentiation circuits and integration circuits, which voltages are proportional to the positive respectively the negative powers of the frequency. The differentiation circuits and integration circuits respectively are supplied with oscillator voltages such that at their outputs voltages of the correct phase are obtained. The voltages from the differentiation circuits and integration circuits are added via summing resistors and are superimposed on the compensation voltage of the oscillator.