I'm designing a class D amplifier and I want to generate a high frequency triangle signal in order to use it for the PWM. I've designed the comparator already and I used a LM2903B IC, because it works well for very high frequencies.

Now I'm trying to generate the triangle signal using the configuration from this page. I've done the calculations using those formulas for a 400 kHz, 1 V peak-to-peak signal:

I added the corresponding resistance values in the circuit and replaced the LM741s shown with LM2903B, which I know are functional models. When I try to run the simulation, I get this:

I tried this circuit again with other resistance values and LM358 op amps instead and the configuration works, it generates a 153 Hz triangle wave:

Then I left the same values and just replaced the LM358 with LM2903B and once again I get nothing:

What am I doing wrong? I suspect the value for Vsat in the calculations is not correct. I took it from the datasheet by subtracting the max input voltage range from the max supply voltage in the Recommended Operating Conditions section. But apart from that, I'm not sure.

Any help is appreciated!