AD8000 .cir emulation not working in LTSPICE

Hi Robz ,

We'll look at this. Would speed things along if you uploaded your schematics.

mike

sure would, but I canny see how, it only allows image/video or link, do I have to make a link, isn't there an upload file?

Hi Robz ,

Easiest to zip up the files and drag to the reply box.

mike

I don't understand why the gain is down at -35db it should  be +10

LTspice_AD8000_circuit1.zip

Hi Robz ,

OK, got the zip. Will run it.

mike

Hi Robz ,

Ah, touché. No symbol. :-) Will create one.

mike

How do you add new parts?  I could only find advice to unzip the app's LIB zip, add the ad800.cir, rezip and copy back into the app folder, can't belive its that user unfriendly!

Robz  Before we start troubleshooting the model, I want to make sure your circuit is behaving as expected with an ideal opamp.

/cfs-file/__key/communityserver-discussions-components-files/1020/Basic-Circuit-with-ideal-opamp.asc

I've redrawn your schematic, with the following changes:

- I've replaced the AD8000 with an ideal opamp

- I've replaced the Rser in the input voltage with an actual resistor - just helps me to visualize.

- I've remove supply bypass caps - not needed for this sim, just trying to simplify as much as I can.

I'm using an input signal with a lower frequency, just to make sure I understand the behavior of the circuit.

The opamp DC bias at In+ is set by the 27k resistor divider to Vcc/2 - that looks fine.

The opamp is going to drive the DC bias of the output to 4.4V - since it's trying to drive that 430 resistor divider connecting to IN- to Vcc/2, to drive the opamp inputs to the same voltage.

Can we work this this simpler schematic to ensure it's behaving as expected before switching out to the more complex macromodel?  One thing that is going to give us trouble when we switch this ideal model with a more realistic model is that the opamp is trying to drive the output to the supply rail.  One possibility is to replace the GND of the 430 resistor divider with VCM = 2.2V?

Robz The .cir file for the AD8000 is available for download on it's product page.  I recommend putting any .cir and symbol files you create in the same directory as your schematic (.asc) file.

/cfs-file/__key/communityserver-discussions-components-files/1020/AD8000-Example.zip

Here's an example using the AD8000 model that I downloaded from the product page.

See my response where I explore this circuit with an ideal opamp.  I suspect that the AD8000 model is working fine, and we just need to figure out how to connect it so that it's worked as expected.

Why didn't you just use the AD8000 model, the circuit is just as simple as using the 5532.

The interface on LTSpice is not exactly intuitive, so its faster for you, someone who knows the tricks, to add the AD8000 than for a new user, me, to set up an alternative op amp.

If you can't add the AD8000 and get it to work, what hope do I have?