Relaxation oscillator

About: Relaxation oscillator is a research topic. Over the lifetime, 1952 publications have been published within this topic receiving 22326 citations.

An Oscillator-Based Active Bridge Circuit for Interfacing Capacitive Sensors With Microcontroller Compatibility

Abstract: This paper deals with the development of a signal conditioning circuit, with microcontroller compatibility, for interfacing capacitive sensors suitable for a wide range of applications. The circuit comprises of a capacitive active bridge, along with a relaxation oscillator for converting capacitance changes into frequency directly. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor and a capacitive transducer for measurement of the dielectric constant of edible oil are reported. The experimental results confirm the theoretical values predicted. The frequency output of the circuit has been used to determine the response characteristics of the trace moisture sensor and the dielectric constants of the edible oils. Finally, the output frequency has been calibrated in terms of the trace moisture in parts per million (ppm), using commercial dew point meter (SHAW, U.K.). The accuracy of moisture measurement using custom designed capacitive sensor for the full-scale moisture range of 4–100 ppm, compared with the dew point meter (accuracy ±0.1%), is found to be nearly ±1% and the resolution is 1 ppm moisture. The circuit is less complex and is easy to integrate to application-specific integrated circuits in a standard CMOS technology with high sensitivity (selectable). It can be easily reproduced with the cheapest possible components, while achieving fairly good performance in terms of both accuracy and dynamic range.

Selective High-Frequency Mechanical Actuation Driven by the VO2 Electronic Instability.

Abstract: Relaxation oscillators consist of periodic variations of a physical quantity triggered by a static excitation. They are a typical consequence of nonlinear dynamics and can be observed in a variety of systems. VO2 is a correlated oxide with a solid-state phase transition above room temperature, where both electrical resistance and lattice parameters undergo a drastic change in a narrow temperature range. This strong nonlinear response allows to realize spontaneous electrical oscillations in the megahertz range under a DC voltage bias. These electrical oscillations are employed to set into mechanical resonance a microstructure without the need of any active electronics, with small power consumption and with the possibility to selectively excite specific flexural modes by tuning the value of the DC electrical bias in a range of few hundreds of millivolts. This actuation method is robust and flexible and can be implemented in a variety of autonomous DC-powered devices.

Garage door opener using transmitter with SAW oscillator modulator

Abstract: A radio frequency (r-f) transmitter has an electric oscillator circuit for producing an oscillating r-f signal in an antenna. A feedback sub-circuit of the oscillator circuit includes a surface acoustic wave (SAW) resonator for stabilizing the oscillations. The feedback circuit has a Q of less than 12000. There is a modulation sub-circuit of the oscillator circuit which includes a voltage variable capacitor. The voltage variable capacitor responds to input voltage variations to modulate the capacitance of the feedback circuit, thereby modulating the frequency of the transmitter. A garage door opener system employing the transmitter is also disclosed.

Current Conveyor Based Relaxation Oscillator with Tunable Grounded Resistor/Capacitor

Abstract: At the outset the foregoing document is represented by square-wave generator using three second generation current conveyers, five resistors and one capacitor with independent control of frequency is presented. The unique features associated with such waveform generator are the easy tunability of frequency over a range of 15 Hz to 150 kHz, extremely low sensitivities as well as suitable for very large scale integration (VLSI) implementation. The working capacity of the proposed circuit is examined with the aid of SPICE models of IC AD 844 AN. Later, the circuit was built with commercially available current feedback operational amplifiers (AD 844 AN), passive components used externally and tested for waveform generation and tunability. Results achieved prove better agreement with the theoretical values. And the non-idealities also are examined.

A Pulse Generator for UWB-IR Based on a Relaxation Oscillator

Abstract: We propose the adaptation of a well-known relaxation oscillator to produce a modulated Gaussian pulse suitable for ultra-wide-band (UWB) impulse radio (IR). The proposed circuit has low area and low power consumption, can easily be modulated by a digital signal, and requires no special technology options; these features make it suitable for UWB-IR low-cost applications. The circuit behavior is confirmed by simulation and by experimental results on a prototype designed in austriamicrosystems 0.35-mum SiGe-BiCMOS technology.