A fast measurement technique for the determination of small signal parameters of the bipolar transistor

The author deals with the measurement of small-signal parameters for modern bipolar transistors. The proposed method uses the measurement of S parameters, mathematical conversion of these S parameters to H parameters, and the circle-fit method. Since modern transistors are to be measured at low DC currents, common base measurements are preferred over common emitter measurements. How the circle-fit method can be used to extract the small-signal parameters is indicated.