I would like to know if there can be any problems when high frequencies(500MHz) pass from the emitter to the collector in a transistor. Example: 2N3904 (NPN).
I know there are a few limits with the frequency on the base, which switch the transistor, but just wanted to know if there is anything you have to keep in mind when letting high frequencies passing from the emitter to the collector.
Best Answer
To "pass through" from emitter to collector, the bipolar is running in common-base configuration which is the fastest way to use a bipolar.
Given the base is not very controlled (the rbb' sits between the base wiring and the actual base region between emitter and collector), I'd expect significant distortion of any high frequency sinwave current.
And you will drive the emitter with a voltage? or with a current?
Hang an inductor from emitter to "gnd" and inject lots of base current through a low value Rbase. The inductor lets the DC_Ibase become DC_Iemitter that exits through the inductor. Now inject your sinwave of current into the emitter, by way of 1nanoFarad cap. [this assumes your current-originator does not need a DC-path; better would be to simply let any DC_pedestal exit thru that Inductor]