On Mon, Oct 30, 2006 at 12:52:15PM +0100, Wojciech Kazubski wrote: > > Do you like more BC547C for higher frequency applications or 2N3904? > > I once did a simulation for some Ronja differential limiting amplifier > > which showed that BC547C is a bit better than 2N3904 because, despite > > it being lazy, it has higher amplification. > > Yo can also use BF240 (SMD variant BF840) if you want to amplify up to some > 50MHz or even BFR91 (SMD=> BFR93) if faster transistors are needed. Those > transistors cannot be used for saturated switching. For such case try old
Does driving the transistor into cutoff but not saturation also count as saturation switching? CL< > 2N2369 or its derivatives (plastic or SMD). But faster the transistor, more > likely it oscillates. > > > > Is it possible to get rid of oscillating transistors by replacing the > > hand-soldered airwire with a SMD on a 2-sided PCB with a ground-plane? > > Very recommended. Use shortest possible connections to ground and try not to > cut the ground plane with traces, especially long. > > > > What is the major cause of oscillations in high-frequency amplifiers? > > Inductance of wires? > > If your circuit oscillates well above the operating frequency it is mainly > due > to inductance of wires plus parasitic capacitances inside the transistor. The > input-output capacitance is major cause of instability of resonant apmlifiers > (RF or IF) In this case oscillations are at or near operating frequency. > Sometimes amplifiers oscillate on LF due to bad supply decoupling. > > > Wojciech Kazubski > > > _______________________________________________ > geda-user mailing list > [email protected] > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
