Karel Kulhavy wrote:
Hello
In my broadband high sensitivity amplifier I have a rail where bases of all
current source transistors are hooked up. Each current source is a transistor
with an emitter resistor which compensates variance in aplification so that
even unmatched transistors produce matched currents.
Do you have any recommendations how to block the current sources from picking
up some garbage from the air and causing oscillation? Should I block the rail
with a single big capacitor against the ground, or use individual capacitor for
each transistor placed between emitter and base?
What sort of transistors are these? Are you seeing oscillations in
practice or is this just a concern prior to seeing any real hardware?
I'd avoid using transistors which are faster than need be. For example,
sticking a 20 GHz device in there may not be a good idea.
If you can tolerate some additional noise, you can stick some resistance
in series with the base if the transistors themselves are oscillating.
If you have some extra capacitance on the emitter and some inductance in
the base circuit (without much extra resistive loss), then it's not too
hard to build an oscillator. Without knowing some more details anything
else would be pure speculation.
-Dan
_______________________________________________
geda-user mailing list
[email protected]
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
