Breaking loop on differential amplifier

This TI precision labs session focuses on stability testing of differential circuits. This video will show how to break the feedback loop for differential circuits to do open-loop gain phase analysis. Additionally, the video will cover how to set up this test using a reusable preconfigured test block so that circuit modification is fast and minimal.
Learn more about the TI Precision Labs - Op Amp Evaluation Module used in the hands-on lab modules
www.ti.com/tool/ti-plabs-amp-evm
Learn more about the National Instruments VirtualBench
www.ni.com/en-us/shop/electron...
Download and install TINA-TI, the preferred simulator used exclusively with TI Precision Labs - Op Amps
www.ti.com/tool/tina-ti
Download the Analog Engineer's Pocket Reference e-book
www.ti.com/amplifier-circuit/...

[@AlexAlex-sc7pz]

Are the values correct? TeraHenry and TeraFarads are ridiculously high

[@glasslinger]

These are simulations only. To do it with real circuitry would be quite a complicated and expensive undertaking!

[@TexasInstruments]

Hi Alex, You are correct that these values are not practical for real-world physical circuits. They are only for simulation. In simulation they allow for the circuit to be closed-loop for DC but for AC the circuit is open loop. The reason the values are set so large, is that the frequency response measurement will work down to very low frequencies ( e.g. 0.001Hz). These large values will in some rare circumstances cause SPICE convergence issues and in that case we normally drop the value by a factor of 10 or 100 and that solves the issue. We have used this approach for quite a few years with a lot of success, but only in SPICE. Thanks for your feedback.

[@mohammedftouni6209]

Tera Henry and Tera farad!

[@TexasInstruments]

Mohammed, We really should have commented on this in the video as other people have the same concern. The values are correct for simulation. In simulation they allow for the circuit to be closed-loop for DC but for AC the circuit is open loop. The reason the values are set so large, is that the frequency response measurement will work down to very low frequencies ( e.g. 0.001Hz). These large values will in some rare circumstances cause SPICE convergence issues and in that case we normally drop the value by a factor of 10 or 100 and that solves the issue. We have used this approach for quite a few years with a lot of success, but only in SPICE. Thanks for your feedback.

[@mohammedftouni6209]

@@TexasInstruments thanks for the clarification.