Could some electronics guru here please clarify this ? The datasheet for the NPN BJT HFA3134(from Renessas Semi.) states: The HFA3134 and HFA3135 are Ultra High Frequency Transistor pairs that are fabricated with Intersil Corporation?s complementary bipolar UHF-1X process. The NPN transistors exhibit an fT of 8.5GHz, while the PNP transi stors have an fT of 7GHz. Both types exhibit low noise, making them ideal for high fre quency amplifier and mixer applications.
Both arrays are matched high frequency transistor pairs. The matching simplifies DC bias problems and it minimizes imbalances in differential amplifier configurations. Their high fT enables the design of UHF amplifiers which exhibit exceptional stability.
The datasheet does not provide any S parameter values for any frequency, and I have successfully SPICE modelled common emitter configuration Colpitts oscillators @ 100,
300, 500 and 750 MHz.However, datasheets for other common RF/microwave BJTs such as BFR92A, BFQ67W BFS17 etc, all contain the common emitter S parameters for the respective BJT. So what is so special about the HFA3134 that allows its use at these high frequencies(the stated fT for HFA3134 is 8 GHz), without use of S parameters.Is
All hints|suggestions are welcome. Thanks in advance.