EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: nbritton on October 16, 2015, 06:11:34 am
-
In the attached picture there is what appears to be randomly laid out components. It's a photo from the teardown of the Rigol DS4000. I doubt this is random, what exactly is going on here, why did they decide to lay it out like this?
-
More importantly, what are the unpopulated components?
Model upgrade? Options?
-
It's high-frequency circuitry, with careful consideration of track length and parasitics. Get into the microwave range and things start looking even weirder...
-
I love it! More circuit boards should be like this! Like a medieval Italian village instead of boring modern planned development. :D
-
I have done similar with high voltage circuits where I had large clearance and creepages to worry about.
-
More importantly, what are the unpopulated components?
Model upgrade? Options?
Yeah I was wondering that myself since I just bought one of these. This was the DS4014 100 MHz model, the community has been able to hack them to 500 MHz, but these missing components have me quite concerned that something essential is missing.
-
More importantly, what are the unpopulated components?
Model upgrade? Options?
Yeah I was wondering that myself since I just bought one of these. This was the DS4014 100 MHz model, the community has been able to hack them to 500 MHz, but these missing components have me quite concerned that something essential is missing.
Sometimes it's the opposite and components are added to roll off the bandwidth. You got to remove those. ;D
-
Wow, pretty funky. Almost as if someone forgot to route it! (j/k) :-DD
-
Look closely, it looks to me like there is a deliberate plane cutout out on all layers under that region, so stray capacitance was probably important to minimise in that area.
Scope inputs are normally specified as 1M || 10pf, which means that minimising the input capacitance is quite critical, and they typically have about 5 decades of variable gain, this is the fun sort of analogue to design....
Regards, Dan.
-
The seemingly random placement is to reduce trace length so that lumped element model can be used. It's one of the ways to avoid or reduce keeping proper trace impedance. If the trace is long you usually need to treat it as a transmission line and use distributed element model for calculations. When trace is very short you may get away without it.
Sent from my HTC One M8s using Tapatalk.