Electronic – How to create a subcircuit in LTspice which is in a txt file

ltspice

I've used LTspice for a long time but I've never made a subckt. When I google "create a LTspice subckt from a txt file", there are no clear steps showing how to do it.

One post said to first change the .txt extension to .subckt then click on some pull-down menu which is in an old version of LTspice and no longer there.

Is there a simple 1,2,3 steps in how to do this?

What I have is a .txt file of a subckt. It's a 4 pin device with several MODELs and SUBCKTs within.

Best Answer

LTspice doesn't care about extensions. Whether the file is a .sub, or .lib, .cir, .txt, or even without extension, it reads the file and if the syntax inside is correct, it will use that file.

Therefore, if your .txt file is already a subcircuit, all you need to do is to add a relevant .lib line inside your schematic, while making sure that you spell the filename properly, say .lib /path/to/some/subcircuit.txt (as you probably know, Windows has a history of hiding extensions, unless manually set otherwise).

If all you need is one subcircuit out of that .txt file, the .lib command ensures that everything inside the file is available in the schematic (as long as everything obeys the syntax). Then simply use the name of the desired .subckt in a symbol of your choice (or a SPICE directive).

Related Solutions

Electronic – hspice to ltspice subcircuit

Your model seems to consist of 2 voltage-controlled voltage sources. The e in e0 and e1 gives that away (in a spice netlist, e is a vcvs) I'm guessing that the max=0.3 min=-0.3 set the minimum and maximum output voltage.

Now let's see if there is a way to do the same but in a syntax that LTspice understands. Find a manual here it is, the interesting bit starts at page 113:

E. Voltage Dependent Voltage Source

yes that is what we need, now check if it will accept options to limit the minimum and maximum voltage. Hmm unfortunately there's nu such option. Bummer, this also explains why your model does not work !

Now there is also a BV (Arbitrary behavioral voltage source) source, see page 101. There are also some examples here. I think it is possible to replicate the model using the BV.

Electronic – LTSpice parametric subcircuit instances

The LTSpice manual gives an example of how to do this:

* calling a subcircuit
*
* This is the circuit
X1 in out 0 divider top=9K bot=1K
V1 in 0 pulse(0 1 0 .5m .5m 0 1m)

* This is the subcircuit
.subckt divider A B C
R1 A B {top}
R2 B C {bot}
.ends divider
.tran 3m
.end

The full syntax is given as:

Syntax: Xxxx n1 n2 n3... <subckt name> [<parameter>=<expression>]

The rules for writing expressions are given in the section of the manual on "arbitrary behavioral voltage and current sources".

Best Answer

Related Solutions

Electronic – hspice to ltspice subcircuit

Electronic – LTSpice parametric subcircuit instances

Related Topic