Adding Third Party Mosfet in LTSpice - Page 1
Forum section: electronics / beginners

author: Nikos A.
author_rank: Regular Contributor
timestamp: December 09, 2019, 10:10:13 pm
content: Hi everyone,I am really new to LTspice and I am trying to insert this Mosfethttps://www.onsemi.com/products/discretes-drivers/mosfets/ntb110n65s3hfThe supplier provides ltspice model.https://www.onsemi.com/support/design-resources/models?rpn=NTB110N65S3HFI downloaded and after extracting the file I found a bunch of .asy files. I copied paste the targeted file into the C:\Users\user\Documents\LTspiceXVII\lib\sym path.After that, I was able to insert the component into the drawing and when I tried to simulate the circuit the following was pop up.I cannot figure out what I am missing... Searching around the web I found that some users include .txt file, other include a .lib file.. I am really confused.I opened the .asy file with a text editor and I couldn't find any parameter of the Mosfet..Any help?

author: hugo
author_rank: Regular Contributor
timestamp: December 10, 2019, 03:20:45 am
content: If you're new to LTspice, then you should take a look here:http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice.htm

author: MagicSmoker
author_rank: Super Contributor
timestamp: December 10, 2019, 11:04:04 am
content: The easiest, most reliable, and most portable way of doing this is to include the model in the schematic itself with an inline .model statement. See the example circuit attached for how to do this. The trick is extracting the relevant bits from manufacturers' model files to put into the inline .model statement if they don't provide models specifically for LTSpice (but a lot do these days). Simon Bramble's website referenced above explains this well.Basically though, you right click while holding the Ctrl key down to bring up the component editor window where you can change the part number to something else, then make sure the .model statement references the same part number and LTSpice will use the inline model rather than look in its library files. You don't want to insert the model into the library itself because LTSpice overwrites those files every time it is updated. It also makes your simulation break if you send it to someone else because they won't have the correct model(s) anymore.

author: mikerj
author_rank: Super Contributor
timestamp: December 10, 2019, 01:51:33 pm
content: Since the LTSpice model is both huge and encrypted in this case, it's better to simply include the model file with the .inc directive.I'm not sure what you are hoping this circuit will do however!

author: Nikos A.
author_rank: Regular Contributor
timestamp: December 10, 2019, 02:14:01 pm
content: Thank you for your answers!!Quote from: mikerj on December 10, 2019, 01:51:33 pmMikerj, with this circuit, I want to turn ON the LED for a certain time as soon as the power is on (something like an indicator, maybe to replace the LED with a buzzer). I want to simulate the circuit in order to calculate the appropriate values of RC in order to turn the LED ON for 3-5sIs there any better solution?

author: Wimberleytech
author_rank: Super Contributor
timestamp: December 10, 2019, 02:54:10 pm
content: QuoteWell, this is a bad solution. The gate of the MOSFET is a floating node. You will be fooled by a SPICE simulation. You have forced the initial conditions on the cap with the .ic directive. Very dangerous. You will be fooled unless you are extremely aware of all circuit parasitics as well as electrostatics on the actual implementation.Every node in a circuit must have some dc path to it except for the rare case of a bridged-capacitor (rarely if ever found in discrete designs).Try this (random values chosen)