Author: John Charles McDonald

Publisher:

Published: 1963

Total Pages: 68

ISBN-13:

A method for calculating the switching time and pulse duration of transistor blocking oscillators operating in the nanosecond time domain is presented. The original theory proposed by Linvill and Mattson is tested using transistors with increasing alpha cutoff frequency. This theory gives close correlation between measured and calculated switching times for low-frequency transistors. For high-frequency units differences as large as an order of magnitude exist. With circuit switching times of less than 10 nsec, a new circuit model is necessary for good theoretical and measured correlation. Small-signal analysis as proposed by Linvill and Mattson adequately describes the circuit operation, and even considering that large signal are involved in the circuit's operation, a large-signal transistor model is necessary only during a description of initial turn-on. Design techniques for minimizing switching time, based on the new circuit models, are presented. A free running oscillator is described with a 6-nsec rise time and a 3-nsec fall time, and design limitations of the blocking oscillator as a nanosecond-pulse generator are presented. The pulse-width determination theory given by Linvill and Mattson is shown to give accurate results if the feed back capacitor is sufficiently large to maintain a constant voltage across the emitter during the output pulse. (Author).