OPA2277: OPA2277&OPA2192 Output characteristics

Hi Koichi-san,

koichi nakahashi said:

OPA2277 may oscillate, but OPA2192 does not,

The circuit description implies that both circuit may be V-I converter type. 

OPA2277 has GBW near 1MHz while OPA2192 has GBW approx. 10MHz. These are two totally different amplifiers. You can not compare the performance of the op amps by generalizing the comparisons. 

The op amp oscillation is related to additional pole presented in your circuit within a closed loop. Typically there is a resistor tied to the NMOS gate, and V-I circuit are sensitive to additional poles generated via Vgs and Vgd and overall phase lag in the feedback circuit. So the apple to orange comparisons are not applicable in this case. The AC loop analysis performance is needed in order to understand the difference. 

If you are able to provide the schematic, I will be happy to analyze the circuit, and provide you the reasons about the root causes why one is oscillate (in OPA2277) and one is not in OPA2192.  

If you have other questions, please let me know. 

Best,

Raymond

Thank you for your reply.
Please let me know if there are any PCN notifications for factory changes or process changes for OPA2277UA between 2022 and 2025. Thank you in advance.
Best regards.

Hi Koichi-san,

koichi nakahashi said:

any PCN notifications for factory changes or process changes for OPA2277UA between 2022 and 2025.

Yes, OPA2277UA is issued the following PCN on 3/7/23. This implies that the current OPA2277UA is post-PCN Si design (likely, if the pre-PCN inventory is depleted.), and the output characteristics are slightly different from pre-PCN OPA2277UA product. 

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/5042/PCN20230228008.1.pdf

All op amps are sensitive to drive capacitive load, weather or not is parasitic or actual capacitive load at output ( Cload value depends on the op amp's output characteristics). However, if the op amp is properly compensated, it will work fine for the application. 

If you can show me the schematic, I can compensate the OPA2277UA's feedback loop for the V-I application. 

If you have other questions, please let me know. 

Best,

Raymond

Thank you very much for sharing the PCN information.

Please note that for confidentiality reasons, we cannot disclose the circuit diagram.

Additionally, please allow me to confirm the following.

-You said that the output characteristics after the PCN are slightly different from the OPA2277UA product before the PCN, but does that mean that the output impedance and reactance have changed?

-Would it be possible for you to disclose the specific numerical values ​​that have changed?

Best regards.