Measurement of transistor hybrid-parameters

The low-frequency transistor hybrid parameters, hi’ ho’ hr andhf’ either common base or common emitter, can easily be found byusing standard equipment such as a Birtcher unit, or from directmeasurements based ,.’n the circuits of Figs. 2.1 and 2.2. The hyb r’Ld+rrelement values, rx’ rTr’ r~, ro and gm at a given operating point canthen be determined reasonably accurately from the above measurements.Once these elements are known, they can then be utilized to determinethe values of CTr and C~ indirectly.TVo main objectives are kept in mind with regard to thesemeasurements. First, the frequency at which these measurements are made should be sufficiently low (up to 3-MHz) so that the equipmentavailable in our Electronics Laboratory can be utilized. Second, themeasurement should be easy to make, and yet reliable and repeatable.It is the purpose of this work to measure the hybrid parametersof a transistor, from which the hybrid-Tr elements rx’ rTr’ r~, ro andg are determined. Because there is no direct method of measuringthe capacitive elements CTr and C~, a simple indirect method is devisedwhereby the values of these capacitive elements can be determined.To minimize cumbersome arithmetic and also to improve accuracy, ashort computer program has been written so that the values of CTr andc~ can readily be calculated (see Appendix A).