OPA657: How to simulate inverting amplifier circuit open loop by TINA-TI?

hurry he

Part Number: OPA657
Other Parts Discussed in Thread: TINA-TI

Hi Team,

I want to get loop gain Bode by TINA-TI. The precision lab video taught the non-inverting amplifier circuit like this picture.

But I can't figure out how to build the circuit to simulate inverting amplifier circuit like this

I would like to know how to break the point and change the signal position to get the Open-loop module. And where to measure feedback value(like Vfb in the first picture)?

Thank you. Best regard.

over 2 years ago

0 Michael Steffes over 2 years ago

Guru 47485 points

Here is a file I had testing Aol, The figure you showed above breaking the loop at the output is slightly in error in that it isolates the open loop output impedance from the feedback network. I look at the 40dB Aol frequency then project that 1pole Aol rollof to GBP by multiplying that F by 100X,

7801.Aol curve generation for VFA op amps OPA657 2016 update.TSC

And then to continue on to a LG sim, follow the steps shown in these two articles,

https://www.planetanalog.com/stability-issues-for-high-speed-amplifiers-introductory-background-and-improved-analysis-insight-5/

https://www.planetanalog.com/stability-issues-and-resolutions-for-high-speed-voltage-feedback-op-amps-insight-6/

+1 SimaJalaleddine over 2 years ago

TI__Mastermind 22270 points

Hello Hurry,

It would be the same either way (inverting or non-inverting). The important aspect for open-loop analysis is the circuit's noise gain (this is different than signal gain) which would be the same in either configuration. Michael shows another way to perform open-loop analysis which is breaking the loop at the input rather than at the output.

Thank you,
Sima

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OPA657: How to simulate inverting amplifier circuit open loop by TINA-TI?