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I am taking an electronics for telecommunications class in my senior year of my undergrad engineering degree. Our teacher said we'd be checking results using Cadence's Orcad Pspice. I find the newer Pspice versions a little confusing and difficult to work with so I asked if I could use TINA-TI, which I used for circuits using transistors in previous courses and found it just fine, but our teacher said that some simulators have less accurate models for high frequency and he would rather I use PSpice so all of us have the same results. I've looked a little bit into it (Comparison Between SPICE Simulators) and all of them seem to have the SPICE base, so I guessed I wouldn't have any problem.

My question is: is that really true? What are the models and differences between simulators? Is there an upper frequency limit for TINA-TI where it starts misrepresenting circuits? I remeber reading there is a way to include your own modeles, is that true for TINA-TI?

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rodrigo_mdelc
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The spice language is the same, the solvers are not the same. It goes like this

Graphic or text-> SPICE netlist -> Circuit matrix -> Numerical solver

The circuit matrix and numerical solver make a huge difference. Some are proprietary. The solver has to find the DC operating point for initial conditions and then start a transient simulation. (if you don't find the initial conditions, you'd have to wait for the system to converge, if it has large time constants it wastes time. Or sometimes it might never converge if the system has local convergence). Here is a great article on how all this works.

I prefer LT spice. Why? Because its free and used internally by Linear, that means it has all the features an engineer could want. Check out this article on numerical solvers and LT spice.

I would also go with the spice program you teacher uses, they have to check it and that takes time.

Voltage Spike
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    So many of the simulators are built on top of Dr. Nagel's original work? Is a Linux analogy appropiate? Say SPICE is the kernel and simulators (TINA-TI, PSpice, LT spice) are the different distros, like Debian, Red Hat or Arch. – rodrigo_mdelc Feb 14 '17 at 23:34
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    Yes, most everyone took the spice2/spice3 code and either modified it or replicated its features. Here is the [original spice page](https://bwrcs.eecs.berkeley.edu/Classes/IcBook/tools.html) – Voltage Spike Feb 14 '17 at 23:43