Semiconductor diodes and triodes are widely used in the practice of geophysical instrumentation, which allow to significantly increase the efficiency, reduce the size and weight of the equipment. However, semiconductor devices, having high performance qualities, at the modern level of production technology are characterized by a scatter of parameters. Therefore, when designing critical nodes of equipment it is necessary to select diodes and especially triodes according to their electrical properties. The most complete idea about amplifying properties of transistors gives the analysis of their output characteristics. Since the process of taking characteristics by points is labor-intensive, there are devices that allow visual observation of the output characteristics of transistors on the oscilloscope screen. Such devices are made in the USSR and abroad in various modifications depending on the range of solved tasks and the required accuracy of observations. Relatively universal units have a complex electronic circuit, simpler ones, as a rule, provide the possibility of only qualitative assessment of amplifying properties of transistors ...