Noise, Fourier analysis and Signal Chain content in TINA-TI(TM) simulator
In this video, the signal chain content that is built into TINA-TI is shown. Examples of Noise analysis and a Fourier analysis are shown on typical signal chain circuits.
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Welcome to this video tutorial for TINA-TI, the free SPICE simulator from Texas Instruments. In this video, we're going to take a look at signal chain products and the features for them in TINA-TI. We will look specifically at a noise simulation and a Fourier series representation.
Signal chain content commonly refers to any components that are found in the fast-moving signal path of a circuit. This includes op amps, comparators, DACs, ADCs, and other signal processing devices. Let's take a look at the signal chain content that's built into TINA-TI.
We click on the SPICE macros tab, click on the Op Amp button. And we can see in the operational amplifiers, we have 685 built in operational amplifier models. For different amplifiers, we have 18 models built in. For fully differential amplifiers, we have 30 models built in. And for instrumentation amplifiers, we have another 29 products. This is just some of the signal chain content that is built into TINA-TI.
Let's take a look at a noise simulation. I'll open an example circuit. In this case, we're using the OPA 363. We're going to simulate using the noise analysis and compare it to the datasheet results that are shown in the schematic.
But first, let's verify that the model actually models noise. To do this, enter the macro and check for the Model Feature section in the macro. Input voltage noise and input current noise are listed as modeled features. Not all signal chain products have noise modeled in them, so you must verify that noise is modeled in your signal chain product before running a noise analysis if you expect the analysis to have meaningful results.
Let's run the noise analysis. Simply select Analysis, Noise Analysis. Here we can configure the start and infrequency of the noise analysis. In this case, we're going to leave it at 10 Hertz to 100 kilohertz, as that's what the datasheet plot has shown.
We're going to take a look at input noise and total noise. The simulation is run, and the sweep is now present. However, it doesn't look much like the datasheet plot. That's because the y-axis is in different scale and different values. Let's change that and do a better comparison.
We're going to change the scale to logarithmic. We're going to change the lower limit to 10 nano. We want to change the upper limit to 1,000. Now you'll see there's a good matching between the plot and the plot from the datasheet.
If we take a look at the total noise, it is also represented here. However, we don't have a datasheet plot to compare to. I'm going to open another circuit so we can run a Fourier analysis on it. I'm going to open one of the example files. In the Oscillator section, I'm going to open a 500 kilohertz square wave and sine wave circuit. I'm going to run a transient analysis to verify the performance. We have a sine wave, and we have a square wave.
Let's take a look at the Fourier analysis of this circuit. To do that, we select for Fourier Analysis, Fourier Series. A window pops up allowing us to change the sampling start time, the base frequency, the number of samples, and the number of harmonics as well as choosing which output we'd like to use. In this case, I'm going to use the sine wave.
I'm also going to change the number of harmonics to 8. I'm going to increase the number of samples to 16,000. The base frequency is going to become 500 kilohertz.
I click Calculate to calculate the Fourier coefficients. Fourier coefficients are now shown here, as is the harmonic distortion. It's fundamental that the user understand what the Fourier series and Fourier analysis is doing. The easiest way to do this is to click on the Help button.
The Help button explains all of the different fields and all of the different formats that are being used in this particular tool. Please refer to it for specific questions on how the Fourier series coefficients are derived. You can also click on Draw. Draw creates the FFT graphical plots. 1x the fundamental frequency seems to have the most content, which makes sense, since this was a 500-kilohertz sine wave that had been generated.
In this video, we've taken a quick tour of the signal chain content that's provided in TINA-TI. We also ran a noise analysis and compared it to the datasheet for that particular product. Finally, we ran a Fourier series, created the coefficients, and took a look at the results for the Fourier analysis. Thank you for your attention.