Relaxation oscillator

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

Barkhausen criterion and another necessary condition for steady state oscillations existence

Abstract: Recent times have given rise to interesting discussions about the necessary and sufficient criteria for steady state oscillations of electronic circuits. The aim of this paper is to point out that the Barkhausen criterion (Bc), while a necessary condition for oscillations, but not a sufficient one, could be supplemented with another necessary condition. Here, we would like to take account of a feature of phase vs. frequency characteristics of linear feedback networks for oscillators. We analyze Twin-T (DT) oscillator and modified Wien (MW) oscillator according to [6], [7], from the point of linear circuit theory by means of open loop characteristic equations and root-locus diagrams for some parameters values where derivatives of the phase vs. frequency open loop feedback systems can be positive or negative, (in the vicinity of the frequencies where the Bc is fulfilled). Characteristic equations of both oscillators and their root-locus diagrams as a function of gain of ideal linear amplifier (AMP) are compared and estimated. For nonlinear amplifier, nonlinear ordinary differential equations have been solved and compared with the assistance of MATLAB, MathCAD and MICRO-CAP (MC10). In addition, we present experimental investigation of the impact of phase vs. frequency characteristic properties on steady state oscillation existence in feedback oscillators in other article as well [15]. All obtained results have confirmed that feedback systems with positive derivatives of phase vs. frequency characteristics (in the vicinity of frequencies where Bc is fulfilled) are incapable of producing steady state oscillations. So we can say that the requirement for negative derivatives of phase vs. frequency characteristic of the feedback network could be understood as a necessary condition for oscillations existence. It is a novel look at the role of this characteristic for steady state oscillations existence.

Drift compensated digitally tuned voltage controlled oscillator

Abstract: A compensated digitally tuned voltage controlled oscillator includes a voltage controlled oscillator circuit that is driven by a digital to analog converter The digital to analog converter receives a digital input and converts it to a voltage to which the voltage controlled oscillator circuit will respond A feedback circuit is connected between a digital input circuit and the output of the voltage controlled oscillator circuit and includes a comparator having one input connected to receive the output of the voltage controlled oscillator circuit and a second input connected to receive the output of a reference oscillator which is also provided The output of the comparator is connected to influence the data that is applied to the digital to analog converter and to compensate for variations due to temperature and component aging

Large amplitude operation of the nonlinear oscillator

Abstract: A two-parameter oscillator equation is obtained from the inverse tangent approximation to the amplifier function. The equation accounts for the exponential wave shape of relaxation oscillations, which cannot be explained by van der Pol's equation.

Novel Signal Conditioning Circuit for Push-Pull Type Capacitive Transducers

Abstract: A novel signal conditioning circuit suitable for push-pull type capacitive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the physical quantity being measured even when the transducer output has an inverse relationship with the measurand. The push-pull type capacitive transducer becomes an integral part of a relaxation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. The various sources of error in the circuit are analyzed, and quantitative expressions to estimate such errors are derived. Results obtained from tests on a prototype indicate that the circuit possesses very low errors

Voltage controlled oscillator with linear characteristic

Abstract: A voltage controlled oscillator is provided with an LC parallel resonance circuit connected to the collector of one of a differential pair of transistors, and an amplifier and a capacitor which are connected between the collector of the one transistor and the base of the other transistor. The bases of the differential pair of transistors are equally biased. The emitters of the transistors are connected to a variable current source. The variable current source produces a current proportional to the square of control voltage. The frequency of the VCO can be changed by the control voltage with good linearity over a wide dynamic range. The variable current source causes the VCO characteristic to be linear. The value of the capacitor can be small, making the oscillator circuit well suited for integrated circuit fabrication.