Hi all,
I've got a bit of spare time with exams out of the way and I thought I'd look into some LNA design for fun.
I came across the BFP842ESD, which interested me for having such as low noise factor. Datasheet here: http://www.infineon.com/dgdl/Infine...n.pdf?fileId=db3a3043394427e401394df03a3a27c9
I then looked at their information sheet regarding a test setup here: http://www.infineon.com/dgdl/AN322.pdf?fileId=db3a30433f565836013f57081aaf0275
I'd like to, at some point, look at recalculating values for operation at 1.4GHz, but I have a few questions before then. Firstly, does anyone have any reasons as to why they chose in the second link, to bias the transistor with a simple base bias? Wouldn't this be potentially unstable and have a shifting operating point? Why not something like a potential divider bias? Secondly why is there no emitter bypass cap?
I understand that you guys weren't (maybe!) the designers of this circuit, but may have some insight into this microwave circuit design. Was this circuit just meant to be whisked up quickly, or are there real design benefits to the points above?
Many thanks,
Sparky
I've got a bit of spare time with exams out of the way and I thought I'd look into some LNA design for fun.
I came across the BFP842ESD, which interested me for having such as low noise factor. Datasheet here: http://www.infineon.com/dgdl/Infine...n.pdf?fileId=db3a3043394427e401394df03a3a27c9
I then looked at their information sheet regarding a test setup here: http://www.infineon.com/dgdl/AN322.pdf?fileId=db3a30433f565836013f57081aaf0275
I'd like to, at some point, look at recalculating values for operation at 1.4GHz, but I have a few questions before then. Firstly, does anyone have any reasons as to why they chose in the second link, to bias the transistor with a simple base bias? Wouldn't this be potentially unstable and have a shifting operating point? Why not something like a potential divider bias? Secondly why is there no emitter bypass cap?
I understand that you guys weren't (maybe!) the designers of this circuit, but may have some insight into this microwave circuit design. Was this circuit just meant to be whisked up quickly, or are there real design benefits to the points above?
Many thanks,
Sparky