[time-nuts] Switching transistors, current sources, nonidealties and noise
kb8tq at n1k.org
Sat Jul 2 13:12:25 EDT 2016
Yes, you can also look at it as “damping” or" de-Q-ing”. You trade off a bit of isolation
for stability. Put another way, the resistor will take the isolation of the stage down a bit.
Another practical point on the stage - you want the base bypass as close to the end of that
resistor as you can get it. You want the resistor right up against the base. Inductance in the
base lead is a really bad thing in this case.
> On Jul 2, 2016, at 1:00 PM, Attila Kinali <attila at kinali.ch> wrote:
> On Fri, 1 Jul 2016 12:28:44 -0400
> Bob Camp <kb8tq at n1k.org> wrote:
>> Real cascode circuits can be built with RF transistors. They also can be simulated.
>> Simulating them with the “standard” models is a PIA. The issue is that the inductance
>> of the package is not de-embedded from the test “socket” as carefully as it might be.
>> There is also the somewhat non-intuitive need to stick a low value resistor in the base.
>> Done properly, they are very reproducible and reasonably insensitive to load.
> Thanks! That resistor in the base did the trick!
> Am I right in the assumption that the resistor gives the transistor
> some negative feedback and thus prevents it from oscillating?
> Attila Kinali
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
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