Graham [M0YCX]VHF Preamplifier for 50-70MHz - Grounded Emitter with Feedback, 14dB - M0YCX https://m0ycx.github.io/posts/VHF-Preamp-14dB-2SC2498/ #hamradio
Ryan - G8RKE@m0ycx Interesting, actually makes a little sense to me now. Still learning though so what's the purpose of the inductor and capacitor?
Hi @2E0RKE, It's a feedback network. in this circuit it is used to stabilise (prevent oscillation) and also to adjust the input and output impedances. You can see the behaviour before & after that network modelled here - https://github.com/M0YCX/ycx_rf_notebooks/blob/master/Amplifiers/feedback/Feedback_Amplifier_Studies/2SC2498.ipynb under headings "2SC2498 Bias:4mA, F:70MHz" vs "2SC2498 Bias:4mA, F:70MHz, with feedback" note the impedances/swr and the stability plots go from red to blue... I'm only learning this stuff too btw - the math is fascinating, if mind blowing at times
@m0ycx I might stick it in the Falstad simulator when I get home this evening.
I can read the diagram and know what the components are, but understanding the how and why is another matter.
I'm determined to get to grips with it even if it take a while.
Simple (I think) is an idea I had to share my radio hands free kit with the 2nd rig in the car. I know what it needs to do, but the how is another matter