Accession Number:

AD0614750

Title:

INVESTIGATION OF RELAXATION OSCILLATIONS IN THERMISTOR-CAPACITOR SYSTEMS,

Descriptive Note:

Corporate Author:

BRITISH COLUMBIA UNIV VANCOUVER

Personal Author(s):

Report Date:

1964-09-21

Pagination or Media Count:

14.0

Abstract:

A thermistor displays negative resistance at low frequencies when biased with a current greater than turnover current, and when shunted by a capacitance in this condition, sustained oscillations are possible. The investigation involved a study of the dynamic properties of these oscillations and their relation to the static properties of the thermistor. The relevant thermistor parameters which were measured included the thermal time constant for which special very-low-frequency techniques were developed. The oscillations were studied over a wide range of capacitance covering the transition from sinusoidal to relaxational type. The voltage extrema and period were measured as functions of capacitance, voltage supply resistance, and operating point. An investigation was made of the features of the differential equations describing the behavior of the system, especially for limit cycles corresponding to relaxation oscillations. The asymptotic form of the cycles was derived for the case where the circuital time constant greatly exceeds the thermal time constant of the thermistor. The complicated nature of the equations precluded a solution in a closed form, and approximative methods were found to be necessary. However, in the case of sinusoidal oscillations of small amplitude, the period can be expressed exactly in terms of the system parameters and this result was confirmed experimentally. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE