Hi, I have a transimpedance amplifier and i want to get a plot of Output current (ac) versus Input current (ac) in one capture spice simulation at a particular frequency. An I versus V curve will give me the dynamic range of the TIA. Can it be done with one simulation.
A TIA accepts a current and turns it into a voltage, not a current.
I'll assume you're using PSpice. You should do two simulations. In one, drive the input with a current pulse. Give the pulse's rise time and fall time some lengthy times so that they act like ramps. Now run a Time Domain (Transient) simulation and see how the ramping output voltage compares with the ramping input current.
In the second simulation, drive the input with an IAC component. Now do an AC Sweep/Noise simulation. Let the frequency sweep over a large range, say, 10 Hz to 100 MHz. You might want to change these limits after you see the results. When the sweep is complete, plot DB(Vout) where Vout is the name you've assigned to the output node. This will tell you what the TIA's wideband behavior is.
Short answer: Yes. We'll ignore that a transimpedance amp has a voltage output. Since you're using Capture, lets assume that you're using PSpice. With PSpice as your spice engine, this is easy using parametric analysis and performance analysis.
You need to do a transient analysis since you're looking for compression versus amplitude. AC analysis won't give you the information you're looking for.
You need to do a parametric analysis which is another setup box in the Analysis Setup menu (Analysis Setup is the Schematics program terminology - find the equivalent in Capture). Set up your parametric analysis to run a bunch of different input amplitudes from small to large.
Run the analysis. You will get lots of plots overlaying another. Those are the plots for each input amplitude value.
This is where PSpice shines... In PSpice (not Crapture), select Trace in the top menu bar. Select "Performance Analysis". Click on Wizard and fill in the blanks. You'll probably want to use "Swing_XRange" which will measure the peak to peak amplitude over a specified time range. This will give you a nice graph of output amplitude versus input amplitude. With enough trickery, you can subtract this from a straight line approximation to see where you get significant deviation from expected.
This is the main reason I like PSpice's graphing capability.
-- Mark
Same here ;-)
...Jim Thompson
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That works, Thank you all.
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