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HF RF Transistor Parameter Extraction for LF

Question asked by Stephen Pflanze on Jun 11, 2019
Latest reply on Jun 18, 2019 by LPP

I am seeking to use this BFU520A transistor:

or one like it to create a 40 MHz transimpedance amplifier of topology described by Phil Hobbs in Figure 9, page 4, of this article: 


I consider the BFU520A because of its very high Ft which means there would still be a lot of gain to do the bootstrapping at 40 MHz.


I seek to optimize the resistor values for the resistors in Figure 9. The data for that transistor does not go down to 40 MHz and below which is where I need it. To optimize my concern is how to determine what Beta, and Base Spreading Resistance, to use from 0 to 40 MHz, as a function of collector current, from the data available. Any suggestions are appreciated.