Need amplifier

[Dennis_Knutson]

You still haven't explained what the heck your project is. You've been asked several times to do this. Whether it's homework or not, can you at least answer the question and why you think you need an amplifier and a resistor. You're not going to get any help at all unless you do that.

[johnsold]

eric,

I have spent some time working on a SPICE interface to LV. There is no good commercial SPICE program for the Mac, so I have been using a free unix port called MacSpice. So far I have written a SPICE output file processer in LV. It reads the file, gives the user a choice of variables to plot and some plotting options (linear, log, etc.). My next step is going to be a pre-processor. It will take a netlist file, add the analysis commands, and send it to the SPICE program via System Exec.vi, all with a nice user interface. At the rate I get to work on side projects, it will probably be ready about the same time as LV22 and SPICE 17!

Lynn

[doha]

Ok well ,,, I have the first part in my project is to do experiment to recognize the components ,, I .e If I put resistor I will get linear line (ohm's law) if i put zener diode I will get knee graph ... I must use one either diode or resistor as a load ...so i need amplifier , diode ,, resistor.. also i am doing interfacing in the same time i have board contain all real components  and i am using keithly pci  board .. Ok?? if u have solution to use mutilism then help me plzzzz but in multisim it doesnot support interfacing!!!  

[johnsold]

If your project just involves a very small number of options, I think you could put together something. Draw the circuit and place the diagram in a picture control. Have one option for the resistor load, one for the diode load, and perhaps one for both loads in parallel. Use a selector (enum or ring) to choose the configuration. Put values for the devices (resistance, zener voltage...) in via numeric controls. Heve the circuit equations pre-programmed for each configuration. Enter values. Calculate and display results.

A much more complex system would use a netlist like SPICE, but then you need to program all the equations and deal with all the convergence issues that SPICE already handles.

Lynn

[Dennis_Knutson]

Are you talking about just physically measuring some devices? If so, that's completely different than some code symbols for amplifiers and resistors. To physically measure some component, you would use LabVIEW to control some sort of voltage or current source and some sort of measurement hardware. If you want to run a simulation, that's where you would have write some code to mimic the behavior. None of that is built into LabVIEW itself.

[Dennis_Knutson]

You might also want to look at SignalExpress. It can link up with spice models and external equipment. The only pci boards it supports though, are from NI.

[SteelStonehenge]

That sounds like a neat project!   I did notice a lot of legacy UNIX spice programs out there.  I imagine they wouldn't take much twiddling to get them to work on OS-X.   I use Intusoft ICAP 4 a lot.  It's got some great automation features, although the commercial version is pretty pricy.  (I use an  eval version at home,which has about 99% functionality. 🙂

eric

[SteelStonehenge]

An amplifier MIGHT look like a simple multiplication function in Shangri-La, but in the real world it's a bit more complicated.  With some care, you can simulate various components with the Math node.  You need to know and understand the transfer curves of various devices, which is how SPICE works.  For example, you can simulate a diode with a logarithmic function.  Over a small region, a diode looks like a square law device...at bigger signals, though, it becomes more linear.  So, really to do it right, you'd need to have some piecewise approximations.

Eric