LTspice Thin Film Resistor Simulation

[Garrick Jardine]

Alright, my question is pretty simple to ask but perhaps rather difficult to solve.

I am modelling in LTspice a channel of previous design and analysing various noise figure across the channel.
Currently I am using the stock resistors supplied in LTspice. I was wondering if there is a way to use a thin film resistor model for more accurate simulation before I start modding the real world circuit and use real world money.

Has anyone had any luck changing the resistor model or know of any models that may have been designed.\

Thank you for your time.
Garrick

 

[ronsimpson]

real world money

LOL

more accurate simulation

spice is only as good as the data. The transistor models are not complete.

On big power resistors I have add the nH of lead inductance. I was working on 100mhz power amplifiers where lead inductance is a factor. (50 watt resistors)
For RF amp application, I have added the nF capacitance to the ground plane. (resistors)
For critical capacitors I add the internal resistance and inductance. (power capacitors at high current and frequency)

These things make the circuit very complicated and the sim-time gets very long.

What are you working on? For most applications I do not do all this work.

 

[crutschow]

Generally a thin film resistor is near perfect as far as noise is concerned, so it would just be the theoretical thermal (Johnson) noise of a resistor, which I think is already modeled in LTspice (but I'm not sure).

 

[Roff]

Check out this LTspice tutorial. It may be helpful. If you already know all this, then I can't help.

 

[simonbramble]

you can specify a noiseless resistor in ltspice. It is not something I have ever done, but you can use one of these, then build up your own noise sources on top of that if needed

http://ltwiki.org/index.php5?title=Undocumented_LTspice