OPA333A-EP: Stability check of OPA333 fully differential amplifier

Hi Kavindu,

The image below is all about biasing voltage and DC operation. I do not know what you are trying to do. There is no AC signal in the schematic. 

OPA333 biasing circuit.TSC

OPA333 2nd stage 08142024.TSC

I do not know why your gains are configured so high, but the circuit is operating in DC now. Please let me know if you need additional assistant. 

Best,

Raymond

Hi Raymond,

Sorry if I have not supplied enough information. This circuit is intended to be used with a strain gage full bridge which is represented by R5,R6,R7,R8  in the design. In fact I'm concerned on the stability analysis of the circuit either in time domain or frequency domain. That is why I attached a current generator with step input. Can you propose any method if what I selected was not ok.

Best Regards,

Kavindu

Hi Kavindu,

Kavindu Ratnayake said:

his circuit is intended to be used with a strain gage full bridge

How about INA333 or similar low voltage instrumentation amplifier. The IA should be similar to OPA333 in Si design. Instrumentation amplifier is used as the standard strain gauge amplifier for the sensing application. The strain gauge may be used in mechanical systems to measure forces such as tension, compression, and torsion etc.. 

ht, tension, stress

We have many other low voltage instrumentation amplifiers to choose from, see the link below. Enclosed two application notes as well. 

https://www.ti.com/amplifier-circuit/instrumentation/overview.html

https://www.ti.com/lit/an/sloa034/sloa034.pdf

https://www.ti.com/lit/ug/tidub00/tidub00.pdf?ts=1723693219183&ref_url=https%253A%252F%252Fwww.google.com%252F

If you tell me the highest voltage available in your PCB design and application type, I may be able to suggest something better or higher performance or other input and output design requirements. 

Best,

Raymond 

Hi Raymond,

Yes, agree with you. But I'm looking for a differential output design where the INA output is single-ended.

Best Regards,

Kavindu

Hi Kavindu,

Here are couple options for FDA output design. These are programmable gain IA.  

https://www.ti.com/lit/po/sbot047/sbot047.pdf?ts=1723693683297&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/lit/ds/symlink/pga855.pdf

If you do not see what you like, we can convert the single ended output to differential output. 

Best,

Raymond

Hi Raymond,

Thanks for suggestions. Please propose how we can convert a single-ended to differential ended. Because that 'd be a good lesson for me.

Best Regards,

Kavindu

Hi Kavindu,

Here is the application note.

https://www.ti.com/lit/an/sbaa265/sbaa265.pdf?ts=1723638589942&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/lit/an/sbaa264a/sbaa264a.pdf?ts=1723638557873&ref_url=https%253A%252F%252Fcn.bing.com%252F

https://www.ti.com/lit/ug/tidu038/tidu038.pdf?ts=1723654108539

I can help you to simulate something tomorrow, if you decided which IA will meet your design requirements. INA849 is the latest ultra low noise IA, but the minimum supply voltage needs to be 8V in single supply, +/-4V in dual supply. We have a wide range of pricing and performance IAs to choose from.  

Best,

Raymond

Hi Kavindu,

Here is another simple way to convert single ended output to differential input, see the simulation. 

THP210 SE to DF Output 08152024.TSC

If you have other questions, please let me know. If our support answered all your questions, please close this thread. 

Best,

Raymond