Measurement of transistor characteristic frequencies in the 20ߝ1000 Mc/s range

Apparatus is described for the rapid determination of the cut-off frequencies, f 1 and f α , of transistors in the 20ߝ1000 Mc/s range. Accurate measurements at these frequencies are made possible by the application of transmission-line techniques to the method of comparing the high-frequency voltages which appear across small resistors connected to two leads of the transistor. Methods are adopted which separate the measuring circuits from the input circuit and make the design of the latter non-critical. The relative accuracy of f 1 and f α measurements is discussed, and it is concluded that the inherently more accurate f 1 measurement should have an error within ±5%, whereas the error in f α is probably 2ߝ3 times higher. A few typical measurements are given.