Measurement of high-frequency equivalent circuit parameters of junction and surface barrier transistors

Methods are described for the determination of the high-frequency parameters of junction and surface barrier transistors and involve, in addition to the knowledge of the usual low-frequency parameters, measurement of the product of Ccand the extrinsic base resistance , itself, and the alpha cutoff frequency fα. A previously described method is used to determine the product , but new methods are described for the measurement of and fα. The measurements are of "bridge" type, involving simple circuit adjustments for a response null at a single frequency. Typical experimental results are given for transistors having fαvalues as high as 85 mc, Ccvalues down to 2.3 pF and ranging from 45 to 400 ohms. The limits quoted for fαand Ccrefer to surface barrier transistors. Comparison with results derived by alternative methods of measurement show good agreement.