Multisim: LT1568 Spice modell, AC simulations

[sebmel]

Hi,

I'm building an input stage to an ADC, and need to do some signal conditioning before sampling. I'm thinking of using LT1568 for Low-Pass filtering, but when doing simulations in Multisim 13.0 I'm not getting the results I'm expecting.

I've provided my schematic, which is configured as a 4-pole LP filter with cut-off frequency at 5 MHz. When simulating it act's as a HP filter for some reason..

I've tried LTSpice and everything works fine, and I've contacted LT (Linear Technology) to get help but they suggest me to stick with LTSpice, which is not ideal for me.

I tried to make my own spice-model from code/description I found on the internet but with no success. Perhaps due to limited knowledge of spice.

Attached is the schematic

Thanks in advance

Sebastian

[gmack]

I couldn't even get it to run without adding a coupling capacitor to the signal source!  I haven't looked at it any further but think you should look again at your resistor values - they seem quite low to me (albeit without looking at the device data sheet).  And, don't trust "AC Analysis" - use the "Instuments" insead!

[gmack · Accepted solution]

Try this.

[sebmel]

Hi,

Thank you for your help!

[gmack]

You're welcome!