A bridge for measuring the a.c. parameters of point-contact transistors

A bridge is described for measuring the a.c. parameters of point-contact transistors at 1 000 c/s for chosen d.c. operating conditions. Essentially the bridge involves the comparison of the transistor with a circuit representation of its a.c. equivalent T-circuit. The elements in this equivalent circuit, represented by variable resistances, are adjusted in turn to equal one of the transistor parameters, a condition indicated by the balancing of a bridge. With the circuit arrangement described it is possible to measure the transistor parameters to an accuracy of approximately ±3%. Particular features of the bridge are its simplicity and speed of operation, the set of four parameters being determined in less than 5 min.