Measurement and interpretation of the FT of planar transistors operating in the inverse mode

The problems of measuring the fT of upward-operating planar transistors are discussed. It is shown that accurate values of fß may be determined by measuring the forward and reverse voltage transfer ratio of the transistor when connected in common-collector configuration. A simple, low-cost experimental system is described which gives excellent results over a wide range of collector currents (1 ¿A to 10¿A). Results are presented for a discrete n-p-n transistor, but the method is also ideally suited to measurements on I2L transistors.