A silicon medium-power transistor for high-current high-speed switching applications

A diffused base, diffused emitter, n-p-n silicon switching transistor has been developed for high-current applications such as switching magnetic memories. The transistor is designed to operate as a switch at the 0.75- ampere level. For a collector current of 0.75 ampere, the large signal current gain is 20 and the saturation voltage drop 4 volts. The breakdown voltages are 75 volts collector-to-base, and 6 volts emitter-to-base. The unit shows fast switching characteristics. The rise, storage, and fall times are each of the order of 0.1 µsec. It has a common emitter unity gain frequency greater than 50 Mc. The transistor employs a localized emitter produced by photoresist techniques and oxide masked diffusion. Lead attachment is accomplished by compression bonding. The silicon wafer is bonded through a molybdenum intermediary to a massive copper stud. The design theory of the device, and the variation of device characteristics with temperature are given. The applicability of this devices to RF amplifier service is also discussed.