INA128: TINA saturation simulation

user6239208

Part Number: INA128

I am simulating a very simple circuit using a ac voltage source and the INA128 (image attached). I find that the amplified voltage can become arbitrarily large (if the input voltage is 1V and G=10000, I find VF1 = 10kV). Is the amplifier saturation not included in the model? If it isn't, is it possible to include it somehow?

over 5 years ago

0 Raymond Zhang1 over 5 years ago

TI__Guru 57101 points

Hello user6239208,

I have included the INA128 Tina simulation and I did not see what you observed. I configured what your input parameters, 1Vpp, Gain=10k, please see the attached file.

If you have further questions, please let us know.

Regards,

Raymond

INA128 12052019.TSC

0 user6239208 over 5 years ago in reply to Raymond Zhang1

Prodigy 40 points

Hello Raymond,

thank you very much for your answer. I have performed a transient simulation using my previous design and your file, and can see the output voltage saturating indeed. However, if instead of a transient simulation I run an AC analysis (to obtain the table of AC results) and I probe Vout manually, I find around 10kV.

Cheers,

Alberto

0 Raymond Zhang1 over 5 years ago in reply to user6239208

TI__Guru 57101 points

Hi Alberto,

I see your point. There is an issue with the model outside of linear operating region in AC nodal analysis. The output should have capped at the supply voltage rail as shown in the Transient plot.

As the Vin increases from 10mV, 100mV, 200mV, 300mV and 500mV, the Vout also increases linearly beyond the supply voltage rail (set R1=505.1 Ohm or G=100), which is incorrect.

Regards,

Raymond

Amplifiers

Amplifiers forum

INA128: TINA saturation simulation