On Tue, 14 Oct 2008 08:35:55 +1300, you wrote: > One trick that has been used for fixed frequency isolation amplifiers > is to use a low Q series tuned LC circuit to short out the resistor > in series with the base at the frequency of interest.
Yes, but when I burn close to 3 Watts / channel and accept two transistor chains to make it possible to get rid of of the transformers that hurt Tom's application, then I won't easily accept new ferrite parts that might spoil that hard won advantage. And all the impedance curves for ferrite beads that I have end at 500 MHz or so and I would need them at 2.5GHz. > Using a suitable ferrite bead instead of the resistor may allow a > lower base to ground impedance at the signal frequency whilst ensuring > transistor stability. > Such instabilities are perhaps one reason why Spectracom and NIST use > much lower ft transistors in their low noise 1-20MHz distribution > amplifiers. The BFG31s have the advantage that I have a reel of them in the drawer and the alternatives are few. Who else but NXP has a 1W PNP SMD wideband transistor in active production? OK. At least TO-5? Killing ft is probably the easiest part, but precise delay comes naturally with large bandwidth. regards, Gerhard dk4xp (who starts thinking about T-coils and ft-doublers :-) Would 1 GHz distribution really be a barrier? Probably not. I have some experience designing 10 GBit/s fiber optic XFP modules and that should work nicely at 5GHz. ) _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
