Transistor Characteristics at Very Low Temperatures

Abstract

Terminal characteristic curves of common-base p-n-p junction transistors at liquid air temperature and liquid helium temperature are given and compared with those obtained at room temperature. As specimens, three p-n-p junction transistors made by different companies have been tested.

A remarkable decrease of the current amplification factor has been observed at liquid helium temperature. Also in order to get the same emitter current, the lower the temperature, the larger is the emitter D.C. voltage required. The values of four parameters, i.e. input, feedback, transfer and output resistances, change with decrease of temperature.

The maximum gain of the transistor decreases with decrease of temperature, but at liquid air temperature the decrease is comparatively small, while at liquid helium temperature considerable decrease occurs.

Instability sometimes occurs at liquid helium temperature under certain operating regions.

The cut-off point of the collector current in the output characteristic curve extends more and more towards greater positive collector voltage with decrease of temperature.