Relaxation oscillator

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

Current Build-Up in Avalanche Transistors with Resistance Loads

Abstract: A transient analysis for the avalanche transistor is carried out through the use of a diffusion model described in terms of charge variables. Basically, the current as a function of time is calculated by taking the gradient of the minority carrier charge stored in the base region. Two methods of approximating the distribution of stored charge are described. Good agreement has been obtained between calculated and experimental results; it is found that the rise time for the resistance-load case is about four times that for a capacitance-load case which produces the same peak current. A practical pulse generator circuit is described in which the resistance load takes the form of a delay-line. The performance of this circuit is compared with that of a capacitance-load relaxation oscillator; while the rise time of the former is longer, the pulse shape is more easily controlled.

Oscillator synchronizing system for eliminating static phase errors

Abstract: Non-inverting amplifier, with bandpass filter in regenerative feedback path, forms color reference oscillator in a color TV receiver. Phase shift circuit, responsive to an oscillator output, supplies signals to a first phase shifted signal amplifier, which shares a load with the non-inverting amplifier, and is subject to control by complementary outputs of a phase comparator functioning to compare the phase of an oscillator output with the phase of incoming color synchronizing bursts. A voltage comparator, responsive to the respective phase comparator outputs, is periodically enabled by field rate keying pulses. The voltage comparator output controls the charging or discharging of a capacitor during the keying intervals. A second phase shifted signal amplifier, responsive to the output of the phase shift circuit, and delivering its output to the oscillator's feedback path, is subject to control in dependence upon a comparison of a control voltage derived from the voltage held by the capacitor with a reference DC voltage.

Variable duty cycle swtiching circuit

Abstract: A magnetically coupled multivibrator is normally prevented from running free due to the presence of a forwardly biased transistor which holds the base electrode of one of the two multivibrator transistors below its level of base-emitter conduction. A variable current source charges a capacitor to a voltage level which cuts off the holding transistor and allows the multivibrator circuit to operate for one cycle, during the latter part of which cycle the capacitor is dumped so that the successive cycles are separated in time by that time necessary to charge the capacitor to the required level and which time is variable according to the charging current. The variable duty cycle thus obtained for the multivibrator circuit controls a voltage or power source whose output is fed back inversely to control the charging current so that a regulated voltage or power output is produced.

Capacitive and resistive sensing based on compensated relaxation oscillator

Abstract: Relaxation oscillator based capacitance and resistance measurements are investigated with a compensation technique. Output oscillation frequency of op-amp based relaxation oscillator changes over a range of capacitance variation. The range of capacitance variation considered for measurement is between 57.1 and 206.4 pF. The output oscillation frequency deviates from the theoretical value due to non-idealities of opamp. A compensation technique has been proposed to reduce the oscillation frequency error observed in output waveform. The performance of the op-amp is evaluated again post compensation. The experimental results are compared with an integrator based relaxation oscillator and comparator configuration. Further, the concept of utilizing the compensated relaxation oscillator for resistance measurement has been experimented. The compensated relaxation oscillator provide the improved performance in oscillation frequency of the waveform. Thus, the compensated relaxation oscillator could be employed for both resistive and capacitive sensing for two different measurements such as temperature and moisture measurements.