On 10/14/2018 11:20 AM, Dr. Ulrich L. Rohde via time-nuts wrote:
Actually the BFT is out of production since quite a while there are more stable and higher Ft devices on the market. 73 de N1UL
How is a higher Ft device more stable? Those attributes would seem to be mutually exclusive. For time nuts purposes, I would submit this is a bad trend. What we want is higher DC beta, not higher Ft. The higher Ft just makes the device want to oscillate. For any designs I do, I put a 100 ohm resistor in series with the collector as an oscillation killer. There is a similar problem with gain block amplifiers having bandwidths into the double digit GHz. I routinely put a 10 pF capacitor directly from input to ground to kill high frequencies. A related problem is that newer devices have lower base spreading resistance. This does help with noise figure but again risks HF oscillations. Rick N6RK _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
