Analysis on the extracted view

Hello All,

Any suggestions  will be very helpful. 

regards

Sidm

Does the device on the schematic have a multiplier or multiple fingers? If so, you're only going to end up probing one of the devices (the stb analysis needs either a probe device - iprobe or vsource - or a single pin of a single device). If that's the case, I think you will need to use the metal resistor approach.

Andrew

Does the device on the schematic have a multiplier or multiple fingers? If so, you're only going to end up probing one of the devices (the stb analysis needs either a probe device - iprobe or vsource - or a single pin of a single device). If that's the case, I think you will need to use the metal resistor approach.

Andrew

thanks a lot for the reply Andrew. Yes the MOSFET has multiplier of 2 and finger=3. I see the extracted view having multiple instantiations of that MOSFET with MM1__1, MM2__2.... MM6__6 notations 

As you mentioned stb analysis needs either a probe device - iprobe or vsource - or a single pin of a single active device. Is there a way to use the Pin of a passive device pin instead of active device for STB analysis ?

Oh, hang-on - I've noticed from your picture above that you've used the Probe Instance (I assume that /I1/MM1/G isn't an instance but a pin). You should have used Probe Terminal (although that still wouldn't have worked because of your m-factor and increased finger count). 

You can use the pin of a passive device pin - it doesn't matter whether it's a passive or an active device. You give it the pin of a device and then (in essence) an iprobe is inserted within the simulator in series with that device pin, and the loop gain is measured through that inserted probe. In other words, there's nothing special you need to do to enable this - provided that you use Probe Terminal. Probe Instance is fine when probing an iprobe or a vsource, but less useful when probing an active device directly because that then uses the device-based algorithm (see "spectre -h stb") which gives you the feedback within the active device rather than a more usual feedback loop. 

The only restrictions on using device pins (when using Probe Terminal) are when using differential and common-mode  stability because they have to (currently) be a leaf device terminal (so it's no good if the device is in a subckt). There are enhancement CCRs to change this behaviour.

Andrew

thanks a lot Andrew for the details. In the past when I tried the Probe Terminal option it wasn't working for me, in the sense that stability analysis form doesn't show the probe terminal after hitting the apply/Ok button. Screenshot below.

Probe terminal text box entry doesn't show in the analysis in test setup : 

I am using IC618 ISR31 and Spectre 21.1 ISR17

regards 

What appears next to the stb line in the list of analyses is just a "summary" of the setup. It's not possible to fully include all details of the analysis setup in a few characters, but it doesn't mean that the settings have not been accepted. It will work - it's just that the function used to try to summarise the setup for visual display hasn't been updated to cope with Probe Terminal. You can still use, and the proof of the pudding is what is in the netlist.

So it almost certainly was working (as this has worked for some time). Never use the summary info next to the analysis as an indication of anything important!

Andrew