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<@U017T7ECQAX> I'm going to be working on some RF ...
# analog-design
t
@User I'm going to be working on some RF related components (gilbert cell, VCO, PLL, etc.). Looking for someone with some asic design background to help me out. I've got board-level radio design experience but no asic.
y
What in particular are you looking for help with?
t
Realizing the circuits with available primitives...for example, which type of FET primitive to choose, placement in the cell, etc.
but I'm open to any help (circuit design, parameter specing, etc.)
y
I see, I would probably recommend just starting a simple 5 transistor operational amplifier. Go from to specs to layout. There are lots of tutorials in written and video form talking through the various steps. Once you've got an idea of the flow you can start branching out to the circuits you're thinking of.
I'm sure people will be happy to answer specific questions as they come up
s
I second yrappt- the classic first tutorial is building an opamp. If you're rusty on sizing, etc., I'd start by reviewing gm/id design techniques (I think http://web02.gonzaga.edu/faculty/talarico/EE406/documents/gmid.pdf gives a decent approach)
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t
thanks for the references...I'll probably start with the Gilbert cell as it's in my list and is as simple and straightforward as a basic opamp (6 FETs and some biasing...a couple of balums if you're feeling feisty)
As far as workflow, I assume my first task would be simulation with spice (I believe the models aren't available yet?) and schematic refinement. Then physical layout of the cell? (non-parameterized so I assume I wouldn't be using something like BAG?) Is magic the tool for that? Does it import a schematic? (I'll need to go through the magic docs eventually, just planning the particular spice and schematic capture tool to use)
t
AFAIK no, magic doesn't import a schematic.
but after layout you go through extraction and LVS checking that compares the extracted netlist of your layout with your reference schematics to check they indeed are the same thing.
My bad, it can actually import a netlist. Not a schematic, so I think you still need to have drawn your cells / primitives but the interconnect between them can be imported for "interactive" routing I guess.
t
so it doesn't matter much which schematic tool I use as long as it generates a netlist
t
It's actually something being evaluated right now which schematic tool is going to be "recommended". But yeah, in theory you could pretty much use any ... ideally it needs to support attributes on symbols (to specify which type of FET, channel width / length, ...)
t
Hmm...I'll have to see if kicad can generate the attributes...if not I'm guessing gEDA has something that will (gschem I think it is?)
y
Most IC layout tools don't have interactive routing like you're used to from PCB tools. You draw the shapes/wires and run LVS and hope they match. I expect magic will be the same.
t
Kicad is one of the tool being considered (although the nightly build, future 6.0 since the schematic format changes) Alternative would be xschem which is more natively oriented for that kind of use.
t
Thanks. I've got a machine at home that generally tracks master for kicad so I can give that a shot.
s
@yrrapt virtuoso xl and above have many features that mimic interactive routing when using the path tool.
obviously, virtuoso is not an option for a hobby user, so for this PDK it will certainly feel different than PCB design.
y
I use virtuoso layout L professionally, unfortunately license costs means XL isn't an option. I've been told its cheaper to to pay the extra hours of work than pay the extra for the XL licenses. A crazy situation. I'm really hoping some tool improvements come from this open sourcing of IC design
j
@Trevor Clarke happy to help in anyway
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