pinductor of anologlib or inductor of PDK in schematic sim ?

spectre pinductor

i noticed the S-parameter and NF were different when i only change the symbol of inductor, between the inductor form anologlib and the inductor form PDK.

so, as to the inductor of anologlib and the inductor form PDK,which one should be used in schematic simulation ?

thank you.

inductor capacitor layout

the inductor model form PDK include the parameters of process .but it's not convenient for circuit adjustment.

lvs analoglib presistor

pinductor in analogLib ismeant to represent *parasitic* inductors obtained from extraction from layout.

inductor in analogLib is a generic model. In principle you should use the PDK inductor, because it's linked to their model.

eldod

n1cm0c said:

pinductor in analogLib ismeant to represent *parasitic* inductors obtained from extraction from layout.

inductor in analogLib is a generic model. In principle you should use the PDK inductor, because it's linked to their model.

Click to expand...

thank you for your reply.
but i don't understand what you said about the pinductor and inductor in analoglib.
i've tested in a circuit using pinductor and inductor in analoglib. but there's no difference in the result. it seems that they are the same.
"from extraction from layout." layout of what ?

presistor schematic

once the circuit layout is done (inductor, capacitors, transistors and interconnect tracks are drawn for the IC mask) the DRC/EXTRACTOR computes the values of the parasitics, and backannotates it into the schematic. the pcapacitor , pinductor, and other p-devices in the analogLib are meant for this, to represent the parasitics which will get their values from the backannotation from the schematics.

if you netlist a extracted view you'll see the pcapacitor devices in the simulation file, for example.

thank you for your reply.
now my question is how to backannotate ?
at present, i make the post-simulation by means of "symbol".
do you mean when i extracted the parasitics , the p-devices will include these parasitics automatically ? and then i can complete the post-sim by using the p-devices ?
thank you.

Re: pinductor of anologlib or inductor of PDK in schematic s

My explanation was a bit incorrect, I did a quick check.

p-devices are used to represent parasitics, and they are created in the extracted view. When these are netlisted for simulation you can see them in the simulator files.

It's possible to back-annotate voltages from the extracted simulation results to the schematic, but it's not possible to back-annotate parasitic values from the extracted view into the schematics. The back-annotation can't create new elements in the schematic, and apparently it can't use the LVS result to relate a presistor in the extracted view to a presistor in the schematic.

p-devices must exist in the analogLib because of the simulation views, which are used to netlist them for the different simulators (eldoD, hspiceD, spice, spectre).

In principle the presistor/pinductor/pdiode/pcapacitor should *not* be used in a schematic. The presistor for example is replaced by a short circuit when the schematic view is netlisted for simulation. Their symbol exists because they actually appear on top of the layout, graphically, in the extracted view.

Sorry for the confusion, I had to dig a bit, since I never use the p-devices in my schematics...

thank you for your reply, n1cm0c.
"it's not possible to back-annotate parasitic values from the extracted view into the schematics. "
so ,we can make the post-simulation only by means of "symbol"?

as to the p-devices, seems i have many things to learn...hehe ...

Re: pinductor of anologlib or inductor of PDK in schematic s

Post-layout simulation is done using the extracted view, where the symbols of the extracted devices appear "graphically" on top of a simplified version of the layout.
the p-devices are created automatically by the DRC/EXTR tool.
One runs simulations using this extracted version, which is not an schematic, but can be netlisted for simulation. For the detailed steps you should check the on-line documentation. the original schematic can only be back-annotated with simulation results, not with extraction results.

Re: pinductor of anologlib or inductor of PDK in schematic s

thank you n1cm0c, but i'm afraid there are misunderstandings between us.
the pinductor i said is shown in the attachment.

Re: pinductor of anologlib or inductor of PDK in schematic s

pinductor (and pdiode, presistor, pcapacitor) have spectre, hspiceD, spice views, which are for generating the description of the device for the simulator.
the symbol view can be used in schematics, but in principle should not.
it is meant to give a graphical representation of the device in the view that the DRC/EXT tool creates from the layout of your circuit.

Example,

create a diff amplifier called OTA, make a schematic view (containing the schematic, the two diff pair device and a current sink device).
Create a symbol view of the diff amplifier OTA, showing input and output pins, and having a triangular drawing to represent the schematic.
Now create a layout of the OTA, drawing the devices, this is the layout view.

OTA has then 3 views => symbol , schematic and layout

If you run the DRC/EXTRACT tool and ask for circuit extraction with parasitics you'll see a new view for the OTA, called extracted (or something similar, depending on the tool that you choose to use).

OTA has then 4 views => symbol, schematic, layout and extracted

The extracted view canbe netlisted and simulated, just like the schematic view.
The p-devices will be created inside the extracted view of OTA.
If you open the extracted view of OTA the p-devices are visible, because they have a symbol view. The symbol view is the graphical drawing of the device.

is this clear now ?

Re: pinductor of anologlib or inductor of PDK in schematic s

thank you for your reply, n1cm0c.
the p-device you said is like the capacitor created by extraction,just like the attachment shows , right?

Re: pinductor of anologlib or inductor of PDK in schematic s

yes, the capacitor drawing you see in the extracted circuit is the symbol view of the device. The p-devices will be shown as in your img.

Re: pinductor of anologlib or inductor of PDK in schematic s

thank you n1cm0c.
now i know exactly what you mean when you said p-device, just like the img in the post i posted: 29 Sep 2007 10:16 ,right ?
but the pinductor or pcapacitor i said are the symbol from the "analogLib",just like the img shows in this attachment:

Re: pinductor of anologlib or inductor of PDK in schematic s

and the inductor of PDK i said in the title is shown in this attachment:

and the problem i encountered is which one to use during the simulation of schematic, pinductor in analogLib or inductor in PDK.
as they inference the S-parameters and NF and so on.
for example, when i replace the pinductor by inductor from PDK in a design of LNA, they have the same value, the S21 changed greatly.
maybe i should use the inductor from PDK when i do the schematic simulation.