Operating Point - Newbie - LTSpice IV

[gianx80]

Hi to all, I know, I'm a newbie and I'm prepairing the only electronics exam in my degree course in engineering. I have to solve this exercise:

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and I want to get the operation point to know all the currents and tensions ... by this way I can check my calculations ... could you explain me how I can do this with ltspice IV?

P.S.
In LTSpice I have two models for NMOS:

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**broken link removed**

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[kalbun]

Just combine together library symbols from the LTSpice library in order to draw your schematics, then run the simulation "DC operating point". You will obtain a list of DC points for all nodes. If you move the cursor on a node, you can also read the DC point on the status bar.
You should be able to find all symbols needed, included current generator. Don't forget to connect a voltage generator for power supply.
Also, be warned that NMOS and NMOS2 (and most library devices) have some default parameters that can be very different from real-world devices. For a more accurate simulation, I suggest you to select one of the real models (right-click on the component to open its context menu)

 

[gianx80]

Ok, I need more help xD. For example, for Vdd which type of model must I use? A battery, an arbitrary behavioral voltage source, a voltage dependent voltage source, a linear current dependent voltage source, a "normal" voltage source? And for the capacitor that tends to inf, which value must I set in the capacitor properties?

 

[kalbun]

For Vdd you must use a normal voltage source. Find the symbol in the library, then set its DC value to the voltage you have in the exercise.
Since you are only interested in DC operating point, you can omit the "infinite" capacitor.

EDIT:

there was something in the back of my mind about your problem... what I wrote is not exact, at least in theory.
The capacitor inductance is \frac{1}{j\omega C } , so when C \to \infty but \omega = 0 (and this is the case while doing DC operating point), the inductance become undefined.
You can then use a more realistic model for the capacitor, considering ESR and EPR and in this case you could model the capacitor with its EPR